ERK1 MAP2 protein kinase

ABSTRACT

The present invention relates to a newly identified family of protein serine/threonine kinases which phosphorylate microtubule-associated protein 2 (MAP2). It is based, in part, on the cloning and characterization of novel MAP2 kinases designated extracellular signal-regulated kinase 1, 2, and 3 (ERK1, ERK2, ERK3) which are expressed in the central nervous system, and on the identification of another ERK family member, ERK4, with antisera. The present invention provides for recombinant nucleic acid molecules and proteins representing members of the MAP2 kinase family, and also for microorganisms, transgenic animals, and cell lines comprising recombinant MAP2 kinase molecules. In additional embodiments of the invention, the present invention provides for methods for assaying cellular factor activity, including, but not limited to, nerve growth factor activity, in which the activation of MAP2 kinase serves as an indicator of cellular factor activity. These methods may be extremely useful in screening compounds for the presence of a desired cellular factor activity. In specific embodiments, compounds which may be useful in the treatment of Alzheimer&#39;s disease, peripheral neuropathies, and diabetes may be identified using the methods of the invention.

This is a file wrapper continuation of application U.S. Ser. No. 08,462,874, filed Jun. 5, 1995, now abandoned, which is a divisional of U.S. Ser. No. 08/178,488, filed Jan. 7, 1994, now abandoned, which is a continuation of U.S. Ser. No. 07/701,544, filed May 16, 1991, now abandoned, which is a continuation-in-part of U.S. Ser. No. 07/532,004, filed Jun. 1, 1990, now abandoned, each of which is incorporated by reference herein in its entirety.

Pursuant to the provisions of 35 U.S.C. §202(c), it is hereby acknowledged that the Government has certain rights in this invention, which was made in part with fund; from the National Institutes of Health.

1. INTRODUCTION

The present invention relates to a newly identified family of MAP2 protein kinases. It is based, in part, on the cloning and characterization of three MAP2 protein kinases, designated ERK1, ERK2, and ERK3, which are expressed in the central nervous system and elsewhere. The present invention provides for recombinant MAP2 kinase nucleic acids and proteins, cell lines and microorganisms comprising recombinant MAP2 kinase molecules, and bioassay methods for detecting the presence of biologically active compounds which utilize recombinant MAP2 kinase molecules.

2. BACKGROUND OF THE INVENTION 2.1. Protein Kinase Cascades and the Regulation of Cell Function

A cascade of phosphorylation reactions, initiated by a receptor tyrosine kinase, has been proposed as a potential transducing mechanism for growth factor receptors, including the insulin receptor (Cobb and Rosen, 1984, Biochim. Biophys. Acta. 738:1-8; Denton et al., 1984, Biochem. Soc. Trans. 12:768-771). In his review of the role of protein phosphorylation in the normal control of enzyme activity, Cohen (1985, Eur. J. Biochem. 151:439-448) states that amplification and diversity in hormone action are achieved by two principal mechanisms, the reversible phosphorylation of proteins and the formation of “second messengers”; many key regulatory proteins are interconverted between phosphorylated and unphosphorylated forms by cellular protein kinases and certain protein phosphatases.

Some hormones appear to transmit their information to the cell interior by activating transmembrane signalling systems that control production of a relatively small number of chemical mediators, the “second messengers.” These second messengers, in turn, are found to regulate protein kinase and phosphatase activities, thereby altering the phosphorylation states of many intracellular proteins, and consequently controlling the activity of enzymes which are regulated by their degree of phosphorylation (see FIG. 1). The receptors for other hormones are themselves protein kinases or interact directly with protein kinases to initiate protein kinase signalling cascades. These series of events are believed to explain the diversity associated with the actions of various hormones (Cohen, 1985, Eur. J. Biochem. 151:439-448; Edelman et al., 1987, Ann. Rev. Biochem. 56:567-613).

Insulin, like most cellular regulators, exerts its effects on many cellular processes through alterations in the phosphorylation state of serine and threonine residues within regulated proteins. Insulin exerts these effects via its receptor, which has intrinsic tyrosine-specific protein kinase activity (Rosen et al., 1983, Proc. Natl. Acad. Sci. U.S.A. 80:3237-3240; Ebina et al., 1985, Cell 40:747-758). Of note, the proteins encoded by several oncogenes are also protein-tyrosine kinases. For example, P68^(gag-ros), a transmembrane transforming protein, bears many similarities to the insulin receptor, sharing 50% amino acid identity (for discussion, see Boulton et al., 1990, J. Biol. Chem. 265:2713-2719).

Nerve growth factor (NGF), a neurotrophic agent necessary for the development and function of certain central and peripheral nervous system neurons, is also believed to influence cellular functions, at least in part, by altering phosphorylation of intracellular proteins. It has been observed that NGF promotes changes in the phosphorylation of certain cellular proteins (discussed in Volonte et al., 1989, J. Cell. Biol. 109:2395-2403; Aletta et al., 1988, J. Cell. Biol. 106:1573-1581; Halegoua and Patrick, 1980, Cell 22:571-581; Hama et al., 1986, Proc. Natl. Acad. Sci. U.S.A. 83:2353-2357; Romano et al., 1987, J. Neurosci, 7:1294-1299). Furthermore, NGF appears to regulate several different protein kinase activities (Blenis and Erikson, 1986, EMBO J. 5:3441-3447; Cremins et al., 1986, J. Cell Biol. 103:887-893; Landreth and Rieser, 1985, J. Cell. Biol. 100:677-683; Levi et al, 1988, Mol. Neurobiol. 2:201-226; Mutoh et al., 1988, J. Biol. Chem. 263:15853-15856; Rowland et al., 1987, J. Biol. Chem. 262:7504-7513). Mutoh et al. (1988, J. Biol. Chem. 263:15853-15856) reports that NGF appears to increase the activities of kinases capable of phosphorylating ribosomal protein S6 (S6 kinases) in the PC12 rat pheochromocytoma cell line, a model system regularly used to study NGF function. Volonte et al. (1989, J. Cell. Biol. 109:2395-2403) states that the differential inhibition of the NGF response by purine analogues in PC12 cells appeared to correlate with the inhibition of PKN, an NGF-regulated serine protein kinase. Additionally, activators of the cyclic AMP dependent protein kinase (PKA) and protein kinase C (PKC) have been reported to mimic some but not all of the cellular responses to NGF (Levi et al., 1988, Mol. Neurobiol. 2:201-226). Miyasaka et al. (1990, J. Biol. Chem. 265:4730-4735) reports that NGF stimulates a protein kinase in PC12 cells that phosphorylates microtubule-associated protein-2. Interestingly, despite the many reports linking NGF with changes in phosphorylation of cellular proteins, analysis of a cDNA sequence encoding a subunit of the NGF receptor which is sufficient for low-affinity binding of liqand has indicated no evidence for a protein-tyrosine kinase domain in the cytoplasmic region of this low affinity receptor (Johnson et al., 1986, Cell 47:545-554).

2.2. MAP2 Protein Kinase

Ribosomal protein S6 is a component of the eukaryotic 40S ribosomal subunit that becomes phosphorylated on multiple serine residues in response to a variety of mitogenic stimuli, including insulin, growth factors and various transforming proteins (for discussion, see Sturgill et al., 1988, Nature 334:715-718). Recently, an activated S6 kinase has been purified and characterized immunologically and molecularly (Ericson and Maller, 1986, J. Biol. Chem. 261:350-355; Ericson et al., 1987, Mol. Cell Biol. 7:3147-3155; Jones et al., 1988, Proc. Natl. Acad. Sci. U.S.A. 85:377-3381; Gregory et al., 1989, J. Biol. Chem. 264:18397-18401). Reactivation and phosphorylation of the S6 kinase occurs in vitro via an insulin-stimulated microtubule-associated protein-2 (MAP2) protein kinase providing further evidence for a protein kinase cascade (Sturgill, 1988, supra; Gregory et al., 1989, supra). MAP2 kinase has been observed to phosphorylate microtubule-associated protein-2 (MAP2) on both serine and threonine residues (Ray and Sturgill, 1987, Proc. Natl. Acad. Sci. U.S.A. 84:1502-1506; Boulton et al., 1991, Biochem. 30:278-286). These observations suggest that key steps in insulin action involve the sequential activation by phosphorylation of at least two serine/threonine protein kinases (Sturgill et al., 1988, Nature 334:715-718; Gregory et al., 1989, J. Biol. Chem. 264:18397-18401; Ahn et al., 1990, J. Biol. Chem. 265:11495-11501), namely, a MAP2 kinase and an S6 kinase. The MAP2 kinase appears to be activated transiently by insulin prior to S6 kinase activation.

The MAP2 kinase phosphorylates S6 kinase in vitro causing an increase in its activity (Gregory et al., 1989, J. Biol. Chem. 264:18397-18401; Sturgill et al., 1988, Nature, 334:715-718); thus, the MAP2 kinase is a likely intermediate in this protein kinase cascade. The finding that phosphorylation on threonine as well as tyrosine residues is required for MAP2 kinase activity (Anderson et al., 1990, Nature, 343:651-653) suggests that it, like many other proteins, is regulated by multiple phosphorylations. The phosphorylations may be transmitted through one or several signal transduction pathways.

In addition to stimulation by insulin, MAP2 kinase activity can be rapidly increased by a variety of extracellular signals which promote cellular proliferation and/or differentiation. In this regard, MAP2 kinase may be equivalent to pp42 (Cooper and Hunter, 1981, Mol. Cell. Biol. 1:165-178), a protein whose phosphotyrosine content increases following exposure to growth factors and transformation by viruses (Rossamondo et al., 1989, Proc. Natl. Acad. Sci. U.S.A. 86:6940-6943) and activation of the v-ros oncogene (Boulton et al., 1990, J. Biol. Chem. 265:2713-2719). For example, MAP2 kinase activity is stimulated in: terminally differentiated 3T3-L1 adipocytes in response to insulin (Ray and Sturgill, 1987, Proc. Natl. Acad. Sci. U.S.A. 84:1502-1506); in post-mitotic adrenal chromaffin cells in response to signals that induce catecholamine secretion (Ely et al., 1990, J. Cell Biol. 110:731-742); in PC12 cells in response to nerve growth factor-induced neuronal differentiation (Volonte et al., J. Cell Biol. 109:2395-2403; Miyasaka et al. J. Biol. Chem. 265:4730-4735) and in T lymphocytes (Nel et al., 1990, J. Immunol. 114:2683-2689). MAP2 kinase(s) are likely to play important roles in signal transduction in many different pathways and in a wide variety of cell types.

Ray and Sturgill (1988, J. Biol. Chem. 263:12721-12727) describes some chromatographic properties of a MAP2 kinase and reports the biochemical characteristics of the partially purified enzyme. MAP2 kinase was observed to have an affinity for hydrophobic chromatography matrices. The molecular weight of the partially purified enzyme was observed to be 35,000 by gel filtration chromatography and 37,000 by glycerol gradient centrifugation. MAP2 kinase activity of chromatographic fractions was found to correlate with the presence of a 40 kDa phosphoprotein detected by sodium dodecylsulfate polyacrylamide gel electrophoresis (SDS-PAGE). MAP2 kinase was observed to have a Km of 7 μM for ATP, and did not appear to utilize GTP. It has been observed that MAP2 kinase requires phosphorylation on tyrosine as well as serine/threonine residues for activity. Ray and Sturgill (supra) cite several problems encountered in the purification of MAP2 kinase, most notably, the presence of contaminating kinases observed to phosphorylate MAP2 in vitro. In addition, only very small amounts of only partially purified protein were available following chromatographic preparation. As discussed supra, Rossomando et al. (1989, Proc. Natl. Acad. Sci. U.S.A. 86:6940-6943) have suggested that MAP2 kinase may be a tyrosine-phosphorylated form of pp42, a low abundance 42-kDa protein which becomes transiently phosphorylated on tyrosine after cell stimulation with a variety of mitogens. Rossomondo et al. (supra) observed that phosphorylation of pp42 and activation of MAP2 kinase occur in response to the same mitogens, that the two proteins comigrate on two dimensional polyacrylamide gels and have similar peptide maps, and that the two proteins copurify during sequential purification on anion-exchange, hydrophobic interaction and gel-filtration media.

3. SUMMARY OF THE INVENTION

The present invention relates to a newly identified family of protein serine/threonine kinases which phosphorylate microtubule-associated protein 2 (MAP2). It is based, in part, on the cloning and characterization of novel MAP2 kinases designated extracellular signal-regulated kinase 1, 2, and 3 (ERK1, ERK2, ERK3) which are expressed in the central nervous system, and on the identification of another ERK family member, ERK4, with antisera. Accordingly, the term “MAP2 kinase” as used herein shall mean a member of the MAP2 family of kinases, including but not limited to ERK1, ERK2, and ERK3.

The present invention provides for recombinant nucleic acid molecules and proteins representing members of the MAP2 kinase family, and also for microorganisms, transgenic animals, and cell lines comprising recombinant MAP2 kinase molecules. In additional embodiments of the invention, the present invention provides for methods for assaying cellular factor activity, including, but not limited to, nerve growth factor activity, in which the activation of MAP2 kinase serves as an indicator of cellular factor activity. These methods may be extremely useful in screening compounds for the presence of a desired cellular factor activity. In specific embodiments, compounds which may be useful in the treatment of Alzheimer's disease, peripheral neuropathies, and diabetes may be identified using the methods of the invention.

4. DESCRIPTION OF THE FIGURES

FIG. 1. Schematic diagram of the relationship between hormone binding to a cellular receptor and consequent changes in the phosphorylation of proteins.

FIG. 2.

A. SDS-PAGE analysis of final Q-Sepharose #2 fractions isolated from NGF-treated or control PC12 cells. Aliquots of fractions obtained from the final purification column (Q-Sepharose#2) were concentrated and then analyzed via 15% SDS-PAGE. Note that fractions containing the most MAP2 kinase activity contained a prominent band (arrow) with a molecular weight of approximately 43,000 kD, as described for the insulin-stimulated MAP2 kinase BSA. Ovalbumin and cytochrome C are presented as size standards.

B. The complete nucleotide sequence (SEQ ID NO:1) of the ERK1 cDNA and its predicted protein product (SEQ ID NO:2). Asterisks denote the residues most conserved among all protein kinases. The sequences of the nine tryptic peptides that were sequenced are underlined. All residues precisely determined by the amino acid sequencing matched the cDNA encoded protein sequence; questionable residues were verified from the cDNA encoded protein sequence. The fourth and seventh peptides indicated represented the minor peptide components described in the text.

FIG. 3. Nucleotide and predicted protein sequences of ERK2 and ERK3 cDNAs and ERK1Ψ pseudogene. Initiation and termination codons are boxed; approximate locations of protein kinase subdomains indicated by roman numerals; asterisks denote residues most conserved among all protein kinases (Ranks et al., 1988, Science 241:42-52); and pound signs denote which of these residues are not conserved in the indicated sequences.

A. Nucleotide (SEQ ID NO:3) and predicted protein (SEQ ID NO:4) sequence of one of the two ERK2 cDNA clones; protein coding region of the other ERK2 cDNA matches exactly, although sequences in the flanking regions diverged.

B. Complete nucleotide (SEQ ID NO:5) and predicted protein (SEQ ID NO:6) sequence of one of two ERK3 cDNA clones analyzed; sequence of the other ERK3 cDNA matches exactly although there were differences in the amounts of flanking sequence.

C. Alignment of partial sequence of ERK1Ψ with the ERK1 nucleotide sequences; only amino acid differences (including the premature termination codon of ERK1Ψ, which is boxed) from the ERK1 protein sequence are indicated. Dashes indicate deletions in both the nucleotide and amino acid sequences.

FIG. 4. Comparison of ERKs with FUS3, KSS1 and human cdc2 protein sequences.

A. Computer-generated alignments (MacVector Computer Analysis Software, International Biotechnologies, Inc., New Haven, Conn.) were visually optimized. Roman numerals indicate subdomains conserved in protein kinases (Hanks et al., 1988, Science 241:42-52). Dots indicate identity to ERK1 sequence, dashes indicate spaces introduced to improve sequence alignments.

B. Percent identities between the sequences aligned in A, determined over the length of the cdc2+sequence; mismatches, insertions and deletions between two sequences all weighted equally.

FIG. 5. Use of ERK1-, ERK2- and ERK3-specific probes provides evidence for additional ERK genes.

A. Specificity of each of the ERK probes (described in Materials and Methods) was demonstrated by hybridizing three triplicate Southern blots, each with linearized plasmids containing the ERK1, ERK2 and ERK3 cDNA inserts (as marked for each lane), with each of the ERK probes as indicated below the blots.

B. Probing of Southern blots containing EcoR1-digested rat and human genomic DNA with each of the ERK-specific probes; sizes of DNA fragments indicted in kilobases.

C. Probing of Southern blots containing rat genomic DNA digested with Bg12, BamH1 and Hind3 with each of the ERK-specific probes; sizes of DNA fragments indicated in kilobases.

FIG. 6. Independent regulation of ERK transcripts in tissues, developmentally, in cultured astroglia and in the P19 embryocarcinoma cell line.

A. Distinct patterns of expression for each of the ERKs within adult nervous system, in adult peripheral tissues, and in placenta. Specific probes for each of the ERKs (see FIG. 3) were hybridized to Northern blots containing 10 μg of RNA from the indicated adult tissues and brain regions. ADR, adrenal; RET, retina; SC.N., sciatic nerve; S.C., spinal cord; A.BR, adult brain; CBL, cerebellum; HBR, hindbrain; MBR, midbrain, DIEN, diencephalon; STR, striatum; HIP, hippocampus; CTX, neocortex; OLF, olfactory bulb; SKIN, skin; HRT, heart; MUS, muscle; LUNG, lung; INT, intestine; KID, kidney; LIV, liver; SPL, spleen; THY, thymus; PLAC, placenta.

B. ERK transcripts are developmentally regulated within the nervous system and in peripheral tissues. Ten μg of total RNA isolated from the indicated developmental stages (E: embryonic day; P:post-natal day; AD: adult) of rat brain, spinal cord, hippocampus (HIPP), liver and heart were compared for hybridization to each of the ERK-specific probes.

C. ERK2 and ERK3 transcripts expressed at low levels in cultured astroglia. Ten micrograms of total RNA from adult rat brain (BRN) or cultured astroglia (AST) probed with each of the ERK specific probes, as indicated.

D. Independent regulation of individual ERK genes during differentiation of P19 embryocarcinoma cells. Ten micrograms of total RNA from adult rat brain or from undifferentiated P19 cell (STEM), retinoic acid-induced (NEUR) or DMSO-induced (MUSC) were used to prepare replicate Northern blots which were probed as indicated. LANGFR signifies a probe for the low-affinity NGF receptor, the GAPDH control probe verifies that equal amounts of RNA were loaded in each lane.

FIGURE 7. Expression of active ERK2 in E. coli.

A. Silver stained gels of equal amounts of protein from lysates of E. coli expressing ERK2 or vector alone. The arrow denotes recombinant ERK2.

B. Immunoblot with antiserum 837 of the same amount of E. coli extracts shown in A and about 40 ng of partially purified ERK1.

C. Silver stain (left) and autophosphorylation (right) of 162, 270, or 540 ng of purified recombinant ERK2.

D. Kinase activity of purified recombinant ERK2 incubated for 0, 15, 30, 45, and 60 minutes with MBP.

FIG. 8. Specificity of antipeptide antibodies.

A. Coomassie blue stain of 100 μg of soluble protein from PC12 cells and adult rat brain.

B. Immunoblot of partially purified ERK1, recombinant ERK2, and 100 μg of soluble protein from PC12 cells, 100 μg of soluble (s) and particulate (p) protein from embryonic brain (EM BR) and adult brain (AD BR) (prepared as described in Boulton et al., 1991, Biochem. 30:278-286) with antiserum 956.

C. Duplicate blot probed with antiserum 837.

FIG. 9. Immunoprecipitation of ³²P-labeled ERK proteins from insulin-stimulated Rat 1 HIRc B cells and NGF-stimulated PC12 cells.

A. ERK1 was immunoprecipitated with antiserum 837 from ³²P-labeled (left) Rat 1 HIRc B cells with (+) or without (−) exposure to insulin and (right) PC12 cells with (+) or without (−) exposure to NGF. Tick marks indicate molecular weight standards of 116, 84, 58, 48.5, 36.5, and 26.6 kDa.

B. As in part A with and without NGF but with denaturing immunoprecipitation.

C. Phosphoamino acid analysis of immunoprecipitated ERK1 from NGF-treated PC12 cells. The positions of the phosphoamino acid standards are noted. After 4 hours of labeling, ERK1 was only phosphorylated on serine in the absence of NGF.

FIG. 10. Imunoblot of immunoprecipitated ERK proteins. ERKs were immunoprecipitated from 1 mg of supernatant protein from insulin-treated (+) or untreated (−) Rat 1 HIRc B cells under denaturing conditions using antiserum 837. The immunoprecipitated proteins were resolved by SDS-PAGE and probed with either antibodies to phosphotyrosine (P-Y) or with ERK antiserum 691. Lanes labeled ERK contain an aliquot of a phenyl-Sepharose fraction containing both ERKs 1 and 2.

FIG. 11. Chromatography of supernatants from NGF-treated or untreated PC-12 cells on Mono Q. 10 mg of protein from supernatants of PC12 cells either untreated or treated with NGF were chromatographed on a Mono Q column. Kinase activity with MBP is shown in the upper panel. Numbered fractions were precipitated and immunoblotted with the indicated antibody, either 956, 837 or antiphosphotyrosine (αP-Y).

5. DETAILED DESCRIPTION OF THE INVENTION

For purposes of clarity of disclosure, and not by way of limitation, the detailed description of the invention will be divided into the following subsections:

(i) cloning of the MAP2 kinase protein;

(ii) identification of additional members of the MAP2 protein kinase family;

(iii) expression of recombinant MAP2 protein kinase;

(iv) generation of anti-MAP2 protein kinase antibodies;

(v) bioassays for MAP2 kinase activation; and

(vi) utility of the invention.

5.1. Cloning of the MAP2 Protein Kinase

According to the present invention, MAP2 protein kinase may be cloned by identifying cloned nucleic acids which contain sequences homologous to known MAP2 kinase sequence, for example, but not limited to, the sequences set forth in FIGS. 2B (SEQ ID NO:1), 3A (SEQ ID NO:3), and 3B (SEQ ID NO:5), and/or contained in plasmids pBS-rERK1, pBS-rERK2, or pBS-rERK3, as deposited with the ATCC and assigned accession numbers 40808, 40809, and 75009 respectively. Alternatively, it may be desirable to obtain such sequence information from purified MAP2 kinase protein.

Purified MAP2 kinase may be obtained from tissues which contain MAP2 kinase activity, including, but not limited to, T lymphocytes, insulin-treated, terminally differentiated 3T3-L1 adipocytes, post-mitotic adrenal chromaffin cells induced to secrete catecholamines, PC12 cells treated with nerve growth factor, brain tissue, or insulin-treated rat 1 HIRc B cells, as well as lower eukaryotes such as sea star and Xenopus laevis oocytes. Purification of MAP2 kinase from PC12 cells appears to parallel purification of MAP2 kinases from insulin treated rat 1 HIRc B cells (FIG. 2A).

In a specific embodiment of the invention, and not by way of limitation, MAP2 kinase may be purified to a large extent, as follows (Boulton et al., 1991, Biochem. 30:278-286). Cells containing MAP2 kinase may be used to prepare a cell free extract comprising a crude preparation of MAP2 kinase. For example, either PC12 cells may be cultured in DME medium containing 10% fetal bovine serum and 5% horse serum, and then, prior to NGF treatment, may be incubated in serum-free medium for about one hour. NGF at a concentration of about 4 mM may then be added, and the cells may be incubated for 5 minutes. Alternatively, insulin-treated Rat 1 HIRc B cells may be used. The medium may then be removed and the cells rinsed and scraped into iced homogenization solution that contains 20 mM p-nitrophenylphosphate, 20 mM Tris-HCl, pH 7.5, 1 mM EGTA, 50 mM sodium fluoride, 50 μM sodium orthovanadate and 5 mM benzamidine (MAP2 kinase). Equal numbers of dishes of untreated cells may desirably be harvested as controls. All further steps are preferably performed at 4° C. Cells may be broken with 30-50 strokes of a Dounce homogenizer and homogenates may be centrifuged at 4000×g for 5 minutes. The supernatants may then be centrifuged at 97,000×g for 60 minutes. The resulting supernatants may then be assayed, preferably immediately, then frozen in liquid nitrogen.

For purification of MAP2 kinase, soluble fractions (225-300 ml) combined from 150 to 200 150-cm² dishes of insulin-treated Rat 1 HIRc Bell cells may be adjusted to a conductivity of 3.5 mS (with water) and to concentrations of 40 μM cAMP, 0.5 mM phenylmethylsulfonylfluoride and 0.1 μM pepstatin prior to chromatography on a Q-Sepharose column (1.5×19 cm). The column may be washed with 4 to 5 volumes of buffer A (10% glycerol, 25 mM Tris-HCl, pH 7.5, 50 μM sodium orthovanadate, 1 mM dithiothreitol, 50 mM NaF, 20 mM β-glycerol phosphate, 1 mM EGTA, 10 mM benzamidine, 10 mM p-nitrophenylphosphate, 0.5 mM phenylmethylsulfonyl fluoride, and 0.1 μM pepstatin) containing 40 μM cAMP. Protein may then be eluted by a gradient of 0-0.4 M NaCl in buffer A. Fractions containing stimulated MAP2 kinase activity may be pooled and applied to a phenyl-Sepharose column (1.5×18 cm). The column may then be washed with 5 column volumes of buffer A containing 0.25 M NaCl and protein may be eluted with a descending gradient of 0.25-0.025 M NaCl plus an ascending gradient of 0-65% ethylene glycol in buffer A without glycerol. Kinase activity may be pooled from the phenyl-Sepharose column and applied directly to a 5 ml column (1.5×3 cm) of S-Sepharose followed by a 5 ml column of phosphocellulose (1.5×3 cm). In both cases, unadsorbed material containing MAP2 kinase activity and 2 column volumes of wash may be collected. The MAP2 kinase activity from the phosphocellulose column may be applied directly to a QAE-Sepharose column (1×24 cm). The column may be washed with 5 volumes of buffer A and protein may be eluted with a gradient of 0-0.4 M NaCl in buffer A. The fractions containing MAP2 kinase activity may then be pooled, Brij-58 may be added to give a final concentration of 0.01% (included in all subsequent steps), and the sample may be concentrated by ultrafiltration to 1.5-2 ml in order to load onto an Ultrogel AcA54 column (1×112 cm) equilibrated in buffer A containing 0.2 M NaCl and 0.01% Brij-58. Fractions from the gel filtration column may be collected into tubes containing 2.4 mM leupeptin. The fractions containing activity may be concentrated and diluted with 25 mM Tris, pH 7.5, 1 mM DTT, 10 mM sodium phosphate, 0.1 μM pepstatin, 0.5 mM phenylmethyl sulfonyl fluoride containing 0.01% Brij-58 until the conductivity is reduced to 3 mS and then may be applied to DEAE-cellulose (0.7×18 cm). The activity may be eluted with a gradient of 0-0.25 M NaCl in buffer A. Fractions containing activity may be pooled, and, as necessary, concentrated and diluted as above to apply to either a Mono Q HR 5/5 or a Q-Sepharose (0.5×9 cm) column. The MAP2 kinase activity may be eluted with a gradient of 0-0.25 M NaCl (from Mono Q) in buffer A. Fractions may be assayed and then immediately frozen in liquid nitrogen.

Purified MAP2 kinase may then be digested with trypsin and the resulting peptides subjected to HPLC (Abersold et al., 1987, Proc. Natl. Acad. Sci. U.S.A. 84:6970-6974) as described in section 6.1, infra. The peptides from one of the resulting peaks may then be subjected to a second chromatographic separation. In order to determine fragments of MAP2 kinase protein sequence accurately, it may be necessary to perform repeated purification of peptides and to discriminate between major and minor component peptides, as would be recognized by one skilled in the art.

Peptides may be sequenced by any method known in the art. For example, fractions containing the enzyme may be pooled and final concentrations of 0.05% Lubrol and 8.5% trichloroacetic acid (w/v) may be added to precipitate the protein. After washing with acetone,the protein may be dissolved in electrophoresis buffer and 250 pmol may be loaded onto a 10% polyacrylamide gel in SDS. Protein may be electrophoretically transferred to nitrocellulose (Schleicher and Schuell, Keene, N.H.). The 43 kDa band may be excised for in situ digestion with trypsin (Abersold et al., 1987, Proc. Natl. Acad. Sci. U.S.A. 84:6970-6974), leaving the minor component, which migrates only slightly faster, on the nitrocellulose. Peptides released from the excised piece of nitrocellulose may be subjected to HPLC on a Model 130A chromatography system (Applied Biosystems, Inc., Foster City, Calif.) equipped with a 2.1×100 mm Applied Biosystems RP-300 column. Separations may be performed in 0.1% trifluoroacetic acid at a flow rate of 50 μl/min using a gradient of 0-70% (v/v) acetonitrile of 100-min duration. Absorbency of the eluate may be monitored at 214 nm and the components that eluted may be collected manually. Peptides may be dried onto 1 cm discs of Whatman GF/C paper and sequenced using an Applied Biosystems, Inc. Model 470A amino acid sequencer equipped with a Model 120A phenylthiohydantoin analyzer, according to manufacturer's specifications.

The purification of suitable amounts of MAP2 kinase protein to permit microsequencing makes possible the cloning of a MAP2 kinase cDNA. A strategy for such cloning might be to generate a complementary oligonucleotide probe, based on a segment of known amino acid sequence, and to use this probe to screen cDNA libraries generated from tissue presumed to synthesize mRNA encoding MAP2 kinase as follows. First, the amino acid sequence derived from purified MAP2 kinase protein may be used to deduce oligonucleotide primers which may be generated and used in standard screening techniques or used in polymerase chain reaction (PCR) (Saiki et al., 1985, Science 230:1350-1354). Because of the degeneracy of the genetic code, in which several triplets may specify the same amino acid, several oligonucleotides should be synthesized for a given amino acid sequence, in order to provide for multiple potential nucleotide sequence combinations; the resulting oligonucleotides are referred to as degenerate primers. For example, in a specific embodiment of the invention, a series of degenerate oligonucleotides may be synthesized that correspond to the coding or anti-coding strands for segments of tryptic peptide sequences obtained from purified MAP2 kinase protein. The oligonucleotides may desirably contain non-degenerate tails at their 5′ ends; the tail of each coding strand oligonucleotide may contain, for example, an EcoR1 restriction site, while the tail of each anti-coding strand oligonucleotide may, for example, contain a Sall restriction site. Each coding strand oligonucleotide may then be combined with each anti-coding oligonucleotide in individual PCR reactions using cDNA from Rat 1 cells as template; the PCR reactions and the preparation of the genomic and cDNA templates may then be performed as described in Maisonpierre, C. et al., 1990, Science 247:1446-1451 and Bothwell, A., Yancopoulos, G. and Alt, F., 1990, “Methods for Cloning and Analysis of Eukaryotic Genes”, Jones and Bartlett, Boston, Mass. The amplified product obtained using, for example, the QYIGEG SEQ ID NO:7coding oligonucleotide and the DLKPSN SEQ ID NO:9 anti-coding oligonucleotide (designated QYDL SEQ ID NO:11) may then be isolated using a Sephadex G-50 spin column, digested with EcoR1 and Sall, gel purified using 2% Nusieve (FMC Bioproducts),and subcloned into a vector comprising suitable restriction sites, such as the pGEM4Z vector (Promega).

A suitable library, believed to be likely to contain a MAP2 kinase gene, may then be screened with labeled nucleic acid probe (for example, subcloned PCR product radiolabeled using a PCR-based protocol (Maisonpierre et al., 1990, Science 247:1446-1451)). Examples of a suitable library would include a rat brain or T lymphocyte cDNA library or a cDNA library produced from PC12 cells or post-mitotic adrenal chromaffin cells, to name but a few. Hybridization conditions may be performed as described in Maisonpierre et al. (1990, Science 247:1446-1451) or using any standard techniques; washing of filters may preferably be performed first at low stringency (2×SSC (20 mM sodium citrate, pH 7.0, 0.15 M NaCl), 0.1 SDS at 60° C.) and then at high stringency (0.2×SSC, 0.1% SDS at 60° C.).

Once obtained, a MAP2 kinase gene may be cloned or subcloned using any method known in the art. A large number of vector-host systems known in the art may be used. Possible vectors include, but are not limited to, cosmids, plasmids or modified viruses, but the vector system must be compatible with the host cell used. Such vectors include, but are not limited to, bacteriophages such as lambda derivatives, or plasmids such as pBR322, pUC, or Bluescript® (Stratagene) plasmid derivatives. Recombinant molecules can be introduced into host cells via transformation, transfection, infection, electroporation, etc.

The MAP2 kinase gene may be inserted into a cloning vector which can be used to transform, transfect, or infect appropriate host cells so that many copies of the gene sequences are generated. This can be accomplished by ligating the DNA fragment into a cloning vector which has complementary cohesive termini. However, if the complementary restriction sites used to fragment the DNA are not present in the cloning vector, the ends of the DNA molecules may be enzymatically modified. It may prove advantageous to incorporate restriction endonuclease cleavage sites into the oligonucleotide primers used in polymerase chain reaction to facilitate insertion into vectors. Alternatively, any site desired may be produced by ligating nucleotide sequences (linkers) onto the DNA termini; these ligated linkers may comprise specific chemically synthesized oligonucleotides encoding restriction endonuclease recognition sequences. In an alternative method, the cleaved vector and NAP2 kinase gene may be modified by homopolymeric tailing.

In specific embodiments, transformation of host cells with recombinant DNA molecules that incorporate an isolated MAP2 kinase gene, cDNA, or synthesized DNA sequence enables generation of multiple copies of the gene. Thus, the gene may be obtained in large quantities by growing transformants, isolating the recombinant DNA molecules from the transformants and, when necessary, retrieving the inserted gene from the isolated recombinant DNA.

According to a preferred embodiment of the invention, once a cDNA-derived clone encoding MAP2 kinase has been generated, a genomic clone encoding MAP2 kinase may be isolated using standard techniques known in the art. For example, a labeled nucleic acid probe may be derived from the MAP2 kinase clone, and used to screen genomic DNA libraries by nucleic acid hybridization, using, for example, the method set forth in Benton and Davis (1977, Science 196:180) for bacteriophage libraries and Grunstein and Hogness (1975, Proc. Natl. Acad. Sci. U.S.A. 72:3961-3965) for plasmid libraries. Retrieved clones may then be analyzed by restriction-fragment mapping and sequencing techniques according to methods well known in the art.

Furthermore, additional cDNA clones may be identified from a cDNA library using the sequences obtained according to the invention.

5.2. Identification of Additional Members of the MAP2 Protein Kinase Family

The present invention provides for recombinant nucleic acid molecules corresponding to mammalian nucleic acids which are homologous to the nucleic acid sequences substantially as depicted in FIGS. 2B (SEQ ID NO:1), 3A (SEQ ID NO:3) and 3B (SEQ ID NO:5) or portions thereof of at least 10 nucleotides.

According to the present invention, by screening a DNA library (comprising genomic DNA or, preferably, cDNA) with oligonucleotides corresponding to MAP2 kinase sequence derived either from protein sequence data or from the nucleic acid sequence set forth in FIGS. 2B (SEQ ID NO:1), 3A (SEQ ID NO:3) and 3B (SEQ ID NO:5), clones may be identified which encode distinct members of the MAP2 kinase family, as exemplified in Section 7, infra, in which additional members of the MAP2 kinase family were identified. By decreasing the stringency of hybridization, the chances of identifying somewhat divergent members of the family may be increased. It may also be desirable to use sequences substantially shared by members of the MAP2 kinase family which have been sequenced preferably, for example, sequences from domains V or VI; such highly conserved regions may be particularly useful in identifying additional members of the MAP2 kinase family. Library screening may be performed using, for example, the hybridization technique of Benton and Davis (1977, Science 196:180) or Grunstein and Hogness (1975, Proc. Natl. Acad. Sci. U.S.A. 72:3961-3965). Clones identified by hybridization may then be further analyzed, and new family members may be identified by restriction fragment mapping and sequencing techniques according to methods well known in the art.

It may be desirable to utilize polymerase chain reaction (PCR) technology (Saiki et al., 1985), Science 230:1350-1354) to identify additional members of the MAP2 protein kinase family. For example, sense and antisense primers corresponding to known MAP2 protein kinase sequence (which preferably appears to be conserved among characterized members of the MAP2 protein kinase family) may be used in PCR, with cDNA obtained from cells which produce MAP2 kinase as template. It may be desirable to design these primers such that they include restriction enzyme cleavage sites which may facilitate the insertion of the products of PCR into appropriate cloning vectors. The products of PCR may be inserted into suitable vectors as set forth in Section 5.1, supra, and the resulting clones may then be screened for new family members. Such screening may be performed using standard techniques, including hybridization analysis using probes corresponding to known MAP2 kinase sequence. For example, a series of probes representing different regions of an already characterized MAP2 kinase protein may be hybridized at low stringency to duplicate filters carrying DNA from clones generated using PCR, as outlined above. It may be observed that various clones may hybridize to some probes, but not others. New family members may also be identified by increasing the stringency of the hybridization conditions, wherein new members not identical to probes derived from known members (e.g. ERK1, ERK2 or ERK3) would hybridize less strongly at higher stringency. Alternatively, new family members may be identified by restriction mapping or sequencing analysis using standard techniques to reveal differences in restriction maps or sequences relative to known family members.

5.3. Expression of Recombinant MAP2 Protein Kinase

The present invention provides for recombinant MAP2 protein kinase molecule comprising the amino acid sequence substantially as depicted in FIGS. 2B (SEQ ID NO:2), 3A (SEQ ID NO:4) or 3B (SEQ ID NO:6), or a portion thereof, which has a molecular weight, by SDS-PAGE, of between about 41 and 48 kDa, or about 62-63 kDA, or which comprises a portion homologous to the yeast FUS3 or KSS1 protein kinase as well as a short amino terminal extension or which has a carboxy terminal extension of about 180 amino acids. The present invention also provides for mammalian MAP2 protein kinases homologous to the above-mentioned molecules.

In order to express recombinant MAP2 kinase, the nucleotide sequence coding for a MAP2 kinase protein, or a portion thereof, can be inserted into an appropriate expression vector, i.e., a vector which contains the necessary elements for the transcription and translation of the inserted protein-coding sequence. The necessary transcriptional and translation signals can also be supplied by the native MAP2 kinase gene and/or its flanking regions. A variety of host-vector systems may be utilized to express the protein-coding sequence. These include but are not limited to mammalian cell systems infected with virus (e.g., vaccinia virus, adenovirus, etc.); insect cell systems infected with virus (e.g., baculovirus); microorganisms such as yeast containing yeast vectors, or bacteria transformed with bacteriophage DNA, plasmid DNA, or cosmid DNA. The expression elements of these vectors vary in their strengths and specificities. Depending on the host-vector system utilized, any one of a number of suitable transcription and translation elements may be used.

Any of the methods previously described for the insertion of DNA fragments into a vector may be used to construct expression vectors containing a chimeric gene consisting of appropriate transcriptional/translational control signals and the protein coding sequences. These methods may include in vitro recombinant DNA and synthetic techniques and in vivo recombinations (genetic recombination). Expression of nucleic acid sequence encoding MAP2 kinase protein or peptide fragment may be regulated by a second nucleic acid sequence so that MAP2 kinase protein or peptide is expressed in a host transformed with the recombinant DNA molecule. For example, expression of MAP2 kinase Day be controlled by any promoter/enhancer element known in the art. Promoters which may be used to control MAP2 kinase expression include, but are not limited to, the SV40 early promoter region (Bernoist and Chambon, 1981, Nature 290:304-310), [the CMV promoter] the promoter contained in the 3′ long terminal repeat of Rous sarcoma virus (Yamamoto, et al., 1980, Cell 22:787-797), the herpes thymidine kinase promoter (Wagner et al., 1981, Proc. Natl. Acad. Sci. U.S.A. 78:144-1445), the regulatory sequences of the metallothionine gene (Brinster et al., 1982, Nature 296:39-42); prokaryotic expression vectors such as the β-lactamase promoter (Villa-Kamaroff, et al., 1978, Proc. Natl. Acad. Sci. U.S.A. 75:3727-3731), or the tac promoter (DeBoer, et al., 1983, Proc. Natl. Acad. Sci. U.S.A. 80:21-25), see also “Useful proteins from recombinant bacteria” in Scientific American, 1980, 242:74-94; promoter elements from yeast or other fungi such as the Gal 4 promoter, the ADC (alcohol dehydrogenase) promoter, PGK (phosphoglycerol kinase) promoter, alkaline phophatase promoter, and the following animal transcriptional control regions, which exhibit tissue specificity and have been utilized in transgenic animals: elastase I gene control region which is active in pancreatic acinar cells (Swift et al., 1984, Cell 38:639-646; Ornitz et al., 1986, Cold Spring Harbor Symp. Quant. Biol. 50:399-409; MacDonald, 1987, Hepatology 7:425-515); insulin gene control region which is active in pancreatic beta cells (Hanahan, 1985, Nature 315:115-122), immunoglobulin gene control region which is active in lymphoid cells (Grosschedl et al., 1984, Cell 38:647-658; Adames et al., 1985, Nature 318:533-538; Alexander et al., 1987, Mol. Cell. Biol. 7:1436-1444), mouse mammary tumor virus control region which is active in testicular, breast, lymphoid and mast cells (Leder et al., 1986, Cell 45:485-495), albumin gene control region which is active in liver (Pinkert et al., 1987, Genes and Devel. 1:268-276), alpha-fetoprotein gene control region which is active in liver (Krumlauf et al., 1985, Mol. Cell. Biol. 5:1639-1648; Hammer et al., 1987, Science 235:53-58); alpha 1-antitrypsin gene control region which is active in the liver (Kelsey et al, 1987, Genes and Devel. 1:161-171), beta-globin gene control region which is active in myeloid cells (Mogram et al., 1985, Nature 315:338-340; Kollias et al., 1986, Cell 46:89-94); myelin basic protein gene control region which is active in oligodendrocyte cells in the brain (Readhead et al., 1987, Cell 48:703-712); myosin light chain-2 gene control region which is active in skeletal muscle (Sani, 1985, Nature 314:283-286), and gonadotropic releasing hormone gene control region which is active in the hypothalamus (Mason et al., 1986, Science 234:1372-1378).

Expression vectors containing MAP2 kinase gene inserts can be identified by three general approaches: (a) DNA-DNA hybridization, (b) presence or absence of “marker” gene functions, and (c) expression of inserted sequences. In the first approach, the presence of a foreign gene inserted in an expression vector can be detected by DNA-DNA hybridization using probes comprising sequences that are homologous to an inserted MAP2 kinase gene. In the second approach, the recombinant vector/host system can be identified and selected based upon the presence or absence of certain “marker” gene functions (e.g., thymidine kinase activity, resistance to antibiotics, transformation phenotype, occlusion body formation in baculovirus, etc.) caused by the insertion of foreign genes in the vector. For example, if the MAP2 kinase gene is inserted within the marker gene sequence of the vector, recombinants containing the MAP2 kinase insert can be identified by the absence of the marker gene function. In the third approach, recombinant expression vectors can be identified by assaying the foreign gene product expressed by the recombinant. Such assays can be based, for example, on the physical or functional properties of the MAP2 kinase gene product in bioassay systems as described supra, in Section 5.2. However, if cells containing MAP2 kinase expression constructs contain intrinsic MAP2 kinase, activity resulting from the construct can be distinguished from endogenous kinase activity (e.g. put a distinguishing tag on the recombinant molecule) or by subtracting background levels of endogenous kinase.

Once a particular recombinant DNA molecule is identified and isolated, several methods known in the art may be used to propagate it. Once a suitable host system and growth conditions are established, recombinant expression vectors can be propagated and prepared in quantity. As previously explained, the expression vectors which can be used include, but are not limited to, the following vectors or their derivatives: human or animal viruses such as vaccinia virus or adenovirus; insect viruses such as baculovirus; yeast vectors; bacteriophage vectors (e.g., lambda), and plasmid and cosmid DNA vectors, to name but a few.

In addition, a host cell strain may be chosen which modulates the expression of the inserted sequences, or modifies and processes the gene product in the specific fashion desired. Expression from certain promoters can be elevated in the presence of certain inducers; thus, expression of the genetically engineered NAP2 kinase protein may be controlled. Furthermore, different host cells have characteristic and specific mechanisms for the translational and post-translational processing and modification (e.g., glycosylation, cleavage) of proteins. Appropriate cell lines or host systems can be chosen to ensure the desired modification and processing of the foreign protein expressed. For example, expression in a bacterial system can be used to produce an unglycosylated core protein product. Expression in yeast will produce a glycosylated product. Expression in mammalian cells can be used to ensure “native” glycosylation of the heterologous MAP2 kinase protein. Furthermore, different vector/host expression systems may effect processing reactions such as proteolytic cleavages to different extents.

Once a recombinant which expresses the MAP2 kinase gene is identified, the gene product should be analyzed. This can be achieved by assays based on the physical or functional properties of the product.

Once the MAP2 kinase protein is identified, it may be isolated and purified by standard methods including chromatography (e.g., ion exchange, affinity, and sizing column chromatography), centrifugation, differential solubility, or by any other standard technique for the purification of proteins.

The presence of functional MAP2 kinase activity may be determined as set forth in section 5.5, infra.

5.3.1. MAP2 Gene Kinase Genes and Proteins

Using the methods detailed supra and in Example Sections 6 and 7, infra, the following nucleic acid sequences were determined, and their corresponding amino acid sequences deduced. The sequences of two rat MAP2 kinase cDNAs were determined, and are depicted in FIGS. 2B (SEQ ID NO:l), 3A (SEQ ID NO:3) and 3B (SEQ ID NO:5). Each of these sequences, or their functional equivalents, can be used in accordance with the invention. Additionally; the invention relates to MAP2 kinase genes and proteins isolated from porcine, ovine, bovine, feline, avian, equine, or canine, as well as primate sources and any other species in which MAP2 kinase activity exists. The present invention also provides for ERK4, as identified and described in Section 7, infra, which corresponds to a protein having a molecular weight of about 45 kDa. The invention is further directed to homologous subsequences of MAP2 kinase nucleic acids comprising at least ten nucleotides, such subsequences comprising hybridizable portions of the MAP2 kinase sequence which have use, e.g., in nucleic acid hybridization assays, Southern and Northern blot analyses, etc. The invention also provides for MAP2 kinase proteins, fragments and derivatives thereof, according to the amino acid sequences set forth in FIGS. 2B (SEQ ID NO:2), 3A (SEQ ID NO:4) and 3B (SEQ ID NO:6) or their functional equivalents and for proteins homologous to such proteins, such homology being of at least about 30 percent. The invention also provides fragments or derivatives of MAP2 kinase proteins which comprise antigenic determinant(s) or which are functionally active or which are at least six amino acids in length. As used herein, functionally active shall mean having the capacity to phosphorylate MAP2 or other relevant substrates (e.g. MBP, S6 kinase; see Section 5.5, infra).

For example, the nucleic acid sequences depicted in FIGS. 2B (SEQ ID NO:1), 3A (SEQ ID NO:3) and 3B (SEQ ID NO:5) can be altered by substitutions, additions or deletions that provide for functionally equivalent molecules. Due to the degeneracy of nucleotide coding sequences, other DNA sequences which encode substantially the same amino acid sequence as depicted in FIGS. 2B (SEQ ID NO:2), 3A (SEQ ID NO:4) and 3B (SEQ ID NO:6) may be used in the practice of the present invention. These include but are not limited to nucleotide sequences comprising all or portions of the MAP2 kinase genes depicted in FIGS. 2B (SEQ ID NO:1), 3A (SEQ ID NO:3) and 3B (SEQ ID NO:5) which are altered by the substitution of different codons that encode a functionally equivalent amino acid residue within the sequence, thus producing a silent change. Likewise, the MAP2 kinase proteins, or fragments or derivatives thereof, of the invention include, but are not limited to, those containing, as a primary amino acid sequence, all or part of the amino acid sequence substantially as depicted in FIGS. 2B (SEQ ID NO:2), 3A (SEQ ID NO:4) and 3B (SEQ ID NO:6) including altered sequences in which functionally equivalent amino acid residues are substituted for residues within the sequence resulting in a silent change. For example, one or more amino acid residues within the sequence can be substituted by another amino acid of a similar polarity which acts as a functional equivalent, resulting in a silent alteration. Substitutes for an amino acid within the sequence may be selected from other members of the class to which the amino acid belongs. For example, the nonpolar (hydrophobic) amino acids include alanine, leucine, isoleucine, valine, proline, phenylalanine, tryptophan and methionine. The polar neutral amino acids include glycine, serine, threonine, cysteine, tyrosine, asparagine, and glutamine. The positively charged (basic) amino acids include arginine, lysine and histidine. The negatively charged (acidic) amino acids include aspartic acid and glutamic acid. Also included within the scope of the invention are MAP2 kinase proteins or fragments or derivatives thereof which are differentially modified during or after translation, e.g., by phosphorylation, glycosylation, proteolytic cleavage, linkage to an antibody molecule or other cellular ligand, etc. For example, it may be desirable to modify the sequence of a MAP2 kinase such that specific phosphorylation, i.e. serine threonine, is no longer required or as important.

In addition, the recombinant MAP2 kinase encoding nucleic acid sequences of the invention may be engineered so as to modify processing or expression of MAP2 kinase. For example, and not by way of limitation, a signal sequence may be inserted upstream of MAP2 kinase encoding sequences to permit secretion of MAP2 kinase and thereby facilitate harvesting or bioavailability.

Additionally, a given MAP2 kinase can be mutated in vitro or in vivo, to create and/or destroy translation, initiation, and/or termination sequences, or to create variations in coding regions and/or form new restriction endonuclease sites or destroy preexisting ones, to facilitate further in vitro modification. Any technique for mutagenesis known in the art can be used, including but not limited to, in vitro site-directed mutagenesis (Hutchinson, et al., 1978, J. Biol. Chem. 253:6551), use of TAB® linkers (Pharmacia), etc.

5.4. Generation of Anti-MAP2 Protein Kinase Antibodies

According to the invention, MAP2 kinase protein, or fragments or derivatives thereof, may be used as immunogen to generate anti-MAP2 kinase antibodies. By providing for the production of relatively abundant amounts of MAP2 kinase protein using recombinant techniques for protein synthesis (based upon the MAP2 kinase nucleic acid sequences of the invention), the problem of limited quantities of MAP2 kinase has been obviated.

To further improve the likelihood of producing an anti-MAP2 kinase immune response, the amino acid sequence of MAP2 kinase may be analyzed in order to identify portions of the molecule which may be associated with increased immunogenicity. For example, the amino acid sequence may be subjected to computer analysis to identify surface epitopes which present computer-generated plots of hydrophilicity, surface probability, flexibility, antigenic index, amphiphilic helix, amphiphelic sheet, and secondary structure of MAP2 kinase. Alternatively, the deduced amino acid sequences of MAP2 kinase from different species could be compared, and relatively non-homologous regions identified; these non-homologous regions would be more likely to be immunogenic across various species.

For preparation of monoclonal antibodies directed toward MAP2 kinase, any technique which provides for the production of antibody molecules by continuous cell lines in culture may be used. For example, the hybridoma technique originally developed by Kohler and Milstein (1975, Nature 256:495-497), as well as the trioma technique, the human B-cell hybridoma technique (Kozbor et al., 1983, Immunology Today 4:72), and the EBV-hybridoma technique to produce human monoclonal antibodies (Cole et al., 1985, in “Monoclonal Antibodies and Cancer Therapy,” Alan R. Liss, Inc. pp. 77-96) and the like are within the scope of the present invention.

The monoclonal antibodies for therapeutic use may be human monoclonal antibodies or chimeric human-mouse (or other species) monoclonal antibodies. Human monoclonal antibodies may be made by any of numerous techniques known in the art (e.g., Teng et al., 1983, Proc. Natl. Acad. Sci. U.S.A. 80:7308-7312; Kozbor et al., 1983, Immunology Today 4:72-79; Olsson et al., 1982, Meth. Enzymol. 92:3-16). Chimeric antibody molecules may be prepared containing a mouse antigen-binding domain with human constant regions (Morrison et al., 1984, Proc. Natl. Acad. Sci. U.S.A. 81:6851, Takeda et al., 1985, Nature 314:452).

Various procedures known in the art may be used for the production of polyclonal antibodies to epitopes of MAP2 kinase. For the production of antibody, various host animals can be immunized by injection with MAP2 kinase protein, or fragment or derivative thereof, including but not limited to rabbits, mice, rats, etc. Various adjuvants may be used to increase the immunological response, depending on the host species, and including but not limited to Freund's (complete and incomplete), mineral gels such as aluminum hydroxide, surface active substances such as lysolecithin, pluronic polyols, polyanions, peptides, oil emulsions, keyhole limpet hemocyanins, dinitrophenol, and potentially useful human adjuvants such as BCG (Bacille Calmette-Guerin) and, Corynebacterium parvum.

A molecular clone of an antibody to a MAP2 kinase epitope can be prepared by known techniques. Recombinant DNA methodology (see e.g., Maniatis et al., 1982, Molecular Cloning, A Laboratory Manual, Cold Spring Harbor Laboratory, Cold Spring Harbor, N.Y.) may be used to construct nucleic acid sequences which encode a monoclonal antibody molecule, or antigen binding region thereof.

Antibody molecules may be purified by known techniques, e.g., immunoabsorption or immunoaffinity chromatography, chromatographic methods such as HPLC (high performance liquid chromatography), or a combination thereof, etc.

The present invention provides for antibody molecules as well as fragments of such antibody molecules.

Antibody fragments which contain the idiotype of the molecule can be generated by known techniques. For example, such fragments include but are not limited to: the F(ab′)₂ fragment which can be produced by pepsin digestion of the antibody molecule; the Fab′ fragments which can be generated by reducing the disulfide bridges of the F(ab′)₂ fragment, and the Fab fragments which can be generated by treating the antibody molecule with papain and a reducing agent.

5.5. Bioassays for MAP2 Kinase Activity

The activity of MAP2 kinase may be measured using any suitable kinase assay known in the art. For example, and not by way of limitation, the method described in (Boulton et al., 1990, J. Biol. Chem. 265:2713-2719) as follows. The assay for phosphorylation of MAP2 may contain 30 mM Hepes, pH 8, 50 μM ATP (1-50 cpm/fmol), 1 mM dithiothreitol, 1 mM benzamidine, 10 mM MgCl₂, 100 μg/ml bovine serum albumin, 3 μg MAP2 and no more than about 10 μg sample protein in a final volume of 30 μl for 10 minutes at 30° C. The amount of MAP2 in the assay (100 μg/ml) may be chosen for convenience of analysis both by SDS-PAGE and by precipitation. The enzyme is not saturated with substrate even at 1.36 mg MAP2/ml. However, with 100 μg MAP2/ml enzyme activity may be expected to be linear with time for at least 30 minutes. All samples except for unfractionated supernatants may be routinely assayed as above in the presence of 1 mg of bovine serum albumin. Assays may be terminated by the addition of 10% trichloroacetic acid and precipitates may be collected on glass fiber filters. All assays except as noted above may be terminated by the addition of 0.25 volume of 0.3 M Tris-HCl, pH 6.9, containing 2 M mercaptoethanol, 50% glycerol and 10% SDS and analyzed by electrophoresis in SDS using 5% (MAP2) polyacrylamide gels. The gels may be stained with Coomassie blue, destained in 10% methanol and 10% acetic acid, dried and subjected to autoradiography at −80° C. using Kodak XS-5 or BB-5 film with Dupont Quanta III intensifying screens. Substrate bands may be excised from gels and ³²P may be quantitated using liquid scintillation counting.

5.6. Utility of the Invention

The present invention may be utilized to provide unique model systems for the study of mechanisms of hormones and other cellular factors, and may also be used in methods for screening compounds for hormone/cellular factor activity and to identify agents which function as agonists or antagonists.

According to various embodiments of the invention, recombinant MAP2 kinase molecules can be used to create novel model systems for the study of mechanisms of hormones and other cellular factors. For example, and not by way of limitation, the recombinant molecules of the invention can be incorporated into cells or organisms such that higher than normal amounts of MAP2 kinase are produced, so that the effects of hyperactivation of MAP2 kinase may be evaluated. Overproduction of MAP2 kinase may identify aspects of the hormonal/cellular factor response related to MAP2 kinase activity, particularly when evaluated in comparison to cells or organisms which produce normal amounts of MAP2 kinase.

Alternatively, recombinant MAP2 kinase molecules may be engineered such that cells or organisms comprising the recombination molecules produce a mutant form of MAP2 kinase which may, for example, lack the serine/threonine kinase activity of normal MAP2 kinase. The mutant kinase may, on a concentration basis, overshadow, or titrate out, the effects of normal MAP2 kinase and thereby create cells or organisms with a functional aberrancy of MAP2 kinase function. It is also envisioned that such mutant nucleic acid sequences may result in mutation of the endogenous MAP2 kinase gene, for example, by homologous recombination, creating true MAP2 kinase mutants. In light of the high levels of expression of MAP2 kinase encoding mRNA in the central nervous system, and the role of MAP2 in forming neurofibrillary tangles, it may be possible to generate a transgenic non-human animal which expresses a mutant MAP2 kinase molecule in its central nervous system (e.g. via a brain-specific promoter sequence) and which may serve as an animal model system for neurological disorders such as Alzheimer's disease or for peripheral neuropathies.

In addition, because the present invention enables the production of large amounts of purified MAP2 kinase for the first time, it allows for the production of anti-MAP2 kinase antibodies. Anti-MAP2 kinase antibodies, polyclonal or monoclonal, may be used in experiments utilizing cells or organisms which study the effects of selective neutralization of MAP2 kinase function. Such experiments may further elucidate the specific role of MAP2 kinase in hormone or cellular factor action.

An important embodiment of the present invention relates to methods for the screening of compounds for hormone or cellular factor activity. In specific embodiments, the present invention provides for a method of detecting the presence of a compound having nerve growth factor-like activity comprising (i) culturing cells that produce an NAP2 protein kinase (which is activated by nerve growth factor) in the presence of a compound suspected of having nerve growth factor-like activity (construed to mean activity similar but not necessarily identical to NGF, including, for example, the ability to support the growth of sympathetic neurons in culture) and (ii) detecting changes in the levels of MAP2 protein kinase activity, wherein an increase in activity is indicative of the presence of nerve growth factor-like activity. Similarly, in another specific embodiment, the present invention provides for a method of detecting the presence of a compound having insulin-like activity comprising (i) culturing cells that produce an MAP2 protein kinase (which is activated by insulin) in the presence of a compound suspected of having insulin-like activity (construed to mean activity similar but not necessarily identical to insulin, including for example, the ability to activate MAP2 kinase in insulin, responsive cells) and (ii) detecting changes in the levels of MAP2 protein kinase activity, wherein an increase in activity is indicative of the presence of insulin-like activity. The present invention therefore provides a powerful method for identifying compounds that may be useful in the treatment of diabetes. The present invention also provides for analogous methods which screen for the activity of other hormones or cellular factors. In additional embodiments of the invention, it may be desirable, in the above-mentioned screening methods, to utilize cell lines which comprises a recombinant nucleic acid molecule encoding a mammalian MAP2 kinase, including, but not limited to, recombinant nucleic acid molecules comprising sequences substantially as depicted in FIGS. 2B (SEQ ID NO:1), 3A (SEQ ID NO:3) and 3B (SEQ ID NO:5). Such cell lines may preferably express elevated levels of MAP2 kinase, and would therefore provide a more sensitive assay for MAP2 kinase activation. The present invention also provides for similar methods, in which cells utilized for screening comprise a recombinant nucleic acid sequence homologous to the sequence substantially as depicted in FIGS. 2B (SEQ ID NO:1), 3A (SEQ ID NO:3) and 3B (SEQ ID NO:5) or a portion thereof. The methods of the invention may be used to identify compounds that may be effective in the treatment of peripheral neuropathies or which may promote nerve regeneration. Furthermore, because NGF-responsive cholinergic neurons of the basal forebrain nucleic are consistently affected in early stages of Alzheimer's disease, the methods of the present invention may be particularly useful in identifying compounds with NGF-like activity which may be effective in the treatment of Alzheimer's disease. In addition, such methods may enable the identification of molecules capable of bypassing the hormone/receptor interaction. It may be clinically useful to inhibit the activity of MAP2 kinase in an organism, using, for example, small molecules such as purine analogues.

In further embodiments of the present invention, recombinant MAP2 kinase may be used to identify other molecules, such as kinases related to cellular factor or hormone action. For example, recombinant MAP2 kinase could be used to identify additional kinases by affinity purification, wherein a MAP2 kinase may be used to adhere to other kinases which participate in a MAP2 associated phosphorylation cascade. Sequenced portions of the NGF receptor are likely to be physically associated with an as yet unidentified protein kinase. Recombinant MAP2 kinase may be useful in studying such interactions.

In another embodiment, detecting a change in a MAP2 protein kinase activity resulting from culturing cells in the presence of a compound known to or suspected to affect MAP2 protein kinase activity, can be used to detect the presence or measure the amount of such a compound and its ability to modulate MAP2 kinase activity levels. Such an effect on MAP2 kinase activity can occur directly or indirectly (e.g. through a signal transduction pathway). In a specific example of such an embodiment, the presence of a neurotrophin molecule (including but not limited to NGF, brain derived neurotrophic factor, neurotrophin-3 (NT-3) and other members of the NGF/BDNF/NT-3 family of molecules) can be detected by detecting an increase in the activity of a MAP2 protein kinase upon culturing the cells in the presence of a sample suspected of containing such a neurotrophin molecule. The cells which are cultured in such assays should express receptors for the neurotrophin molecule being detected, which receptors can be endogenous or recombinant.

6. EXAMPLE Molecular Cloning of an Insulin-stimulated MAP2 Protein Kinase: Homology in Pheromone-regulated Cell Cycle Control 6.1. Materials and Methods 6.1.1. Cell Lines

Rat 1 HIRc B cells (McClain et al., 1987, J. Biol. Chem. 262:14663-14671) were obtained from Don McClain (Veterans Administration Medical Center, San Diego, Calif.). Porcine insulin was a gift from Mary Root (Eli Lilly). Restriction enzymes were obtained from New England Biolabs.

6.1.2. Purification and Sequencing of Tryptic Peptides from MAP2 Kinase

MAP2 kinase was purified from insulin-treated Rat 1 HIRc B cells (Boulton et al., 1990, Biochem. 30:278-286), digested with trypsin and the resulting peptides subjected to HPLC (Abersold et al., 1987, Proc. Natl. Acad. U.S.A. 84:6970-6974). The peptides from one of the resulting peaks were subjected to a second chromatographic separation. Amino acid sequence was obtained from seven distinct peaks. One peak contained a mixture of three peptides, with one major and two minor components: the sequence of the major peptide was determined based on recovery, but the assignment of the amino acids in the minor components to their respective peptide sequences was based on the cDNA sequence (see below).

6.1.3. Cloning an Amplified Fragment of the MAP2 Kinase cDNA

A series of degenerate oligonucleotides were synthesized that corresponded to the coding or anti-coding strands for fragments of the tryptic peptide sequences obtained. The oligonucleotides contained non-degenerate tails at their 5′ ends; the tail of each coding strand oligonucleotide had an EcoR1 restriction site, while the tail of each anti-coding strand oligonucleotide contained a Sall restriction site. Each coding strand oligonucleotide was combined with each anti-coding oligonucleotide in individual PCR reactions using rat genomic DNA or cDNA from Rat 1 cells as template; the PCR reactions and the preparation of the genomic and cDNA templates were performed as described in Maisonpierre et al. (1990, Science 247:1446-1451) and Yancopoulous and Alt (1990, in “Methods for Cloning and Analysis of Eukaryotic Genes”, Jones and Bartlett, Boston, Mass.). The amplified product obtained using the QYIGEG SEQ ID NO:7 coding oligonucleotide and the DLKPSN SEQ ID NO:9 anti-coding oligonucleotide (designated QYDL SEQ ID NO:11) was isolated using a Sephadex G-50 spin column, digested with EcoR1 and Sall, gel purified using 2% Nusieve (FMC Bioproducts), and subcloned into the pGEM4Z vector. (Promega).

6.1.4. Screening the cDNA Library

600,000 plaques from a rat brain cDNA library constructed in the Lambda Zap 2 vector (Stratagene) were screened using the subcloned QYDL PCR product as probe; the prove was radiolabeled using a PCR-based protocol described in Maisonpierre et al. Hybridization conditions have been described in Maisonpierre et al.; after hybridization the library filters were first washed at low stringency (2×SSC, 0.1% SDS at 60° C.) and then at high stringency (0.2×SSC, 0.1% SDS at 68° C.).

6.1.5. DNA Sequencing

Sequencing was performed using the dideoxynucleotide chain termination method (Sanger et al., 1977, Proc. Natl. Acad. Sci. U.S.A. 74:5463-5467), with the Sequenase Kit (version 2.0) and recommended protocols (U.S. Biochemical). All sequence was verified by sequencing both strands of the DNA, using appropriate oligonucleotides corresponding to MAP2 kinase sequence or flanking plasmid sequence.

6.1.6. Northern Analysis

RNA isolation, Northern blotting, and hybridization to labeled probes were performed as described in Maisonpierre et al. (1990; Science 247:1446-1451).

6.2. Results

Purified MAP2 kinase isolated from insulin-treated rat 1 HIRc B cells consists of one major band of M_(r)=43,000. SDS polyacrylamide gel electrophoresis of final Q Sepharose #2 fractions isolated from NGF-treated or control PC12 cells indicated that purification of MAP2 kinase from PC12 cells appears to parallel purification of MAP2 kinases from insulin treated rat HIRC B cells (FIG. 2A). Following tryptic cleavage, amino acid sequences of seven tryptic peptides were obtained from the 43 kd band; these peptides are underlined in FIG. 2. None of the peptides are contained in proteins in the Genbank data base. However, consensus sequences characteristic of serine/threonine protein kinases (Hanks et al., 1988, Science 241:42-52), GEGAYG SEQ ID NO:12 (part of the nucleotide binding site) and DLKPSN SEQ ID NO:9 were found among the tryptic peptides isolated from this protein.

Degenerate oligonucleotides corresponding to several different regions of the resulting amino acid sequence were utilized in PCR reactions. Oligonucleotides corresponding to segments of the peptides containing the conserved GEGAYG (SEQ ID NO:12) and DLKPSN SEQ ID NO:9 sequences to segments most clearly yielded amplified fragments of an expected size using cDNA templates prepared from Rat 1 fibroblasts. Based on homologies to other protein kinases it was assumed that the GEGAYG SEQ ID NO:12 sequence is closer to the N-terminus of the protein and DLKPSN SEQ ID NO:9 is closer to the C-terminus of the protein; these sequences are separated by about 120 amino acids in most protein kinases. PCR reactions using the degenerate oligonucleotide encoding the amino acids QYIGEG (SEQ ID No:7) (5′-TTCTAGAATTCCA(A,G)TA(C,T)AT(A,T,C)GG(A,T,C,G)GA(A,G) GG-3′, SEQ ID NO:8) and the degenerate oligonucleotide corresponding to the anti-coding strand for the amino acids DLKPSN (SEQ ID NO:9) (t5′-TTCTCGAGTCGAC(A,G)TT(A,T,C,G)GA(A,T,C,G) GG(C,T)TT(A,T,C,G)A(A,G)A,G)TC-3′, SEQ ID NO:10) yielded an amplified product of approximately 360 bp. The PCR product was subcloned and sequenced to confirm its identity as a novel protein kinase. The PCR product was then used as a probe to screen a rat brain cDNA library. A single clone that hybridizes at high stringency has been isolated; this clone contains a 1.9 kb cDNA insert. Northern blot analysis revealed a band corresponding to a mRNA of 1.9 kb, indicating that the insert corresponded to a full-length clone.

The cDNA insert has a single long open reading frame that could encode a protein of at least 367 residues with M_(r) greater than or equal to 42,000; it contains the primary sequence of seven of the tryptic peptides isolated from the insulin-stimulated MAP2 kinase. In addition, the exact sequences of two additional peptides from a mixed sequence are found in the translated cDNA. Together these tryptic peptides consisted of 115 residues all of which are in accord with sequence in the translated cDNA, accounting for over 31% of the putative translation product. The exact correspondence between the extensive tryptic peptide sequence and the predicted translation product provides substantial evidence that the cDNA encodes the insulin-stimulated MAP2 kinase. We have designated the gene ERK1 for extracellular signal-regulated kinase-1.

ERK1 contains the 15 invariant residues found in all protein kinases; it also displays substantial homology with all of the subdomains defined by Hanks et al. (1988, Science, 241:42-52), and contains residues characteristic of serine/threonine protein kinases. A comparison with other protein kinases reveals striking similarities between MAP2 kinase and the KSS1 (Courchesne, et al., 1989, Cell 58:1107-1119) and FUS3 (Elion, et al., Cell 60:649-664) protein kinases recently isolated from yeast. See infra and FIG. 4. ERK1 kinase is 56% identical to KSS1, and 56% identical to FUS3. KSS1 and FUS3 display about the same degree of similarity (57%) to each other as they do to MAP2 kinase; they are all significantly less homologous to other kinases than they are to each other. All three share their next most impressive homologies with the CDC28/cdc²⁺ subfamily of kinases (ERK1 kinase is 41% identical to this kinase). However, KSS1, FUS3 and MAP2 kinase all lack the VPSTAIR SEQ ID NO:13 sequence found in subdomain III of all CDC28 functional homologs. Furthermore, all three also share C-terminal extensions not found on the CDC28/cdc²⁺ kinases. Unlike FUS3 and KSS1, MAP2 kinase contains a significant N-terminal extension of at least 17 amino acids.

ERK1 also differs from its yeast homologs at the C-terminus and between the DFG and APE motifs of subdomains VII and VIII, which contain inserts of different lengths with phosphorylatable residues (e.g. Thr-238 and Thr-242 in ERK1). Both regions poorly conserved between the yeast kinases, have been implicated in determining unique functional characteristics of individual kinases. In a number of kinases the segment that resides between subdomains VII and VIII is autophosphorylated in a manner that influences enzymatic activity (e.g., cAMP-dependent protein kinases insulin receptor). Conservation among the kinases may also reveal functionally important residues. There is a conserved tyrosine in subdomain 1, whose phosphorylation in CDC28 is known to inhibit protein kinase activity. Near the C-terminus of the protein is a sequence (residues 367-379) that draws particular attention as a potential site of tyrosine phosphorylation due to interesting similarities to the regulatory autophosphorylated region of the insulin receptor. Three tyrosine residues are located within this region spaced identically to those in the receptor (YX₃YY); four acidic residues, important determinants for recognition by protein-tyrosine kinases, are nearby. The presence of sequences resembling the insulin receptor phosphorylation site is consistent with evidence suggesting that ERK1 (MAP2 kinase) may be a substrate for the insulin receptor.

6.2.1. Tissue Distribution and Inducibility of the MAP2 Kinase Transcript

A probe made from the MAP2 kinase cDNA identifies a single 1.9. kb transcript on Northern blot analysis, indicating that our cDNA clone represents nearly full-length transcript. The MAP2 kinase transcript is detectable in all tissues and cell lines examined.

Interestingly, the transcript is expressed at highest levels (by 3- to 6-fold) in the central nervous system compared to other tissues examined. The abundance of MAP2 kinase transcripts in the adult rat brain was estimated to be about 0.0005% by screening 10⁶ phage from a rat brain cDNA library at high stringency. The transcript is clearly detectable in Rat 1 fibroblasts and PC12 cell lines, both of which express acutely activatable MAP2 kinase.

6.3. Discussion

Amino acid sequence was obtained from tryptic peptides isolated from a MAP2 protein kinase purified over 6000-fold from insulin-stimulated rat fibroblasts. The sequence was used to design degenerate oligonucleotides that led to the molecular cloning of a 1.9 kb cDNA via a PCR-based strategy. The cDNA predicts a protein with a molecular weight of greater than or equal to 42,000, designated ERK1, which contains sequences consistent with all of the tryptic peptide sequence obtained from the purified MAP2 kinase, accounting for more than 31% of the primary sequence of the protein. Thus, this cDNA appears to encode the insulin-stimulated MAP2 kinase.

Many protein kinases phosphorylate MAP2 (Aklyama et al., 1986, J. Biol. Chem. 261:14797-14803; Akiyama et al., 1986, J. Biol. Chem. 261:15648-15651; Hernandez et al., 1987, J. Neurochem. 48:84-93). The MAP2 kinase molecularly cloned here is distinguished by its rapid activation by insulin (Boulton et al., 1990, J. Biol. Chem. 265:2713-2719; Ray et al., 1987, Proc. Natl. Acad. Sci. U.S.A. 84:1502-1506; Ray et al., 1988, Proc. Natl. Acad. Sci. U.S.A. 85:3753-3757; Ray et al., 1988, J. Biol. Chem. 263:12721-12727; Hoshi et al., 1988, J. Biol. Chem. 263:5396-5401; Sturgill et al., 1988, Nature, 334:715-718; Anderson et al., 1990, Nature 343:651-653). Although the physiological functions of this enzyme are not known, a role in the regulation of S6 phosphorylation was proposed following the demonstration that MAP2 kinase phosphorylates and activates S6 kinase II purified from Xenopus laevis (Sturgill et al., 1988, Nature 334:715-718) as well as a rabbit liver S6 kinase (Gregory et al., 1989, J. Biol. Chem. 264:18397-18401). The involvement of the MAP2 kinase in signaling pathways is further indicated by the presence of phosphotyrosine on the kinase (Ray et al., 1988, Proc. Natl. Acad. Sci. U.S.A. 85:3753-3757; Boulton et al., 1991, Biochem. 30:278-286; Boulton et al., May 1991, Cell). While it has not been shown that the insulin receptor catalyzes this phosphorylation, the fact that dephosphorylation of the tyrosine residues decreases activity (Anderson et al., 1990, Nature 343:651-653; Boulton and Cobb, May 1991, in Cell Regulation, Vol. II) supports the notion that the MAP2 kinase functions at an early step in the signal transduction pathway and is, therefore, perhaps directly regulated by the insulin receptor. Additional evidence indicating a role for this kinase in signaling by numerous agents is raised by evidence indicating that the MAP2 kinase may be pp42 (Rossomando et al., 1989, Proc. Natl. Acad. Sci. U.S.A. 86:6940-6943), a protein whose phosphotyrosine content increases following transformation by viruses and exposure to growth factors (Cooper et al., 1981, Mol. Cell. Biol. 1:165-178). MAP2 kinase, or a closely related enzyme is also activated by a variety of agents that promote differentiation or expression of differentiated functions, not cellular proliferation (Boulton et al., 1990, J. Biol. Chem. 265:2713-2719; Ray et al., 1987, Proc. Natl. Acad. Sci. U.S.A. 84:1502-1506; Ray et al., 1988, Proc. Nat. Acad. Sci. U.S.A. 85:3753-3757; Ray et al., 1988, J. Biol. Chem. 263:12721-12727; Hoshi et al., 1988, J. Biol. Chem. 263:5396-5401; Ely et al., 1990, J. Cell Biol. 110:731-742; Volonte et al., 1989, J. Cell Biol. 109:2395-2403; Miyasaka et al., 1990, J. Biol. Chem. 265:4730-4735) For example, we have recently purified a nerve growth factor-stimulated MAP2 kinase from PC12 cells to near homogeneity by the same procedure developed to purify the insulin-stimulated enzyme. This enzyme is the same size by SDS-PAGE as the insulin-stimulated kinase. Furthermore, the activity has properties in common with nerve growth factor-activated MAP kinase described by Greene and coworkers (Volonte et al., 1989, J. Cell Biol. 109:2395-2403 and Miyasaka et al., 1990, J. Biol. Chem. 265:4730-4735.

The dramatic homology between ERK1 and the two yeast kinases, KSS1 and FUS3, is consistent with a critical and evolutionarily conserved role for this new family of kinases in mediating the response to extracellular signals. The yeast kinases play antagonistic roles in regulating the yeast cell cycle in response to mating factors, the only known peptide hormones that mediate intercellular communication in yeast. Both kinases seem to act by fine-tuning the activity of CDC28, a related protein-serine/threonine kinase which is the indispensable regulator of the mitotic cycle, probably via interactions with a yeast cyclin. FUS3 apparently has two regulatory roles. It seems to be important in leading to pheromone-induced cell-cycle arrest in G1, either by directly inhibiting the activation of CDC28 or by promoting the inactivation of a cyclin required for CDC28 activation; activation of FUS3 by pheromones also independently promotes mating-specific functions. By contrast, KSS1 promotes re-entry into the cell cycle following pheromone-induced cell-cycle arrest; KSS1 may work by activating the same cyclin that FUS3 may inactivate. ERK1 apparently represents a mammalian counterpart, perhaps functionally as well as evolutionarily, to the yeast kinases. Thus ERK1 may act via similar pathways to regulate the cell cycle in response to a variety of extracellular signals. As with FUS3, ERK1 apparently also plays a regulatory role in responses that do not directly involve the cell cycle. The dramatic homology between ERK1 and the yeast kinases raises the possibility that yeast may provide a useful experimental system in which to introduce ERK1 for the analysis of its function.

MAP2 kinase, or MAP2 kinase-like activity, is increased in many different types of cells in response to a wide variety of stimuli. In the course of cloning ERK1, we have also molecularly cloned other closely related kinases. The identification of a mammalian family of MAP2 kinase-related enzymes, which are structural homologs of the yeast KSS1 and FUS3 kinases, suggests that multicellular, higher eucaryotes have appropriated kinases, originally utilized to detect environmental perturbation by unicellular organisms, to mediate responses to extracellular signals. The molecular cloning of this family of MAP kinase-related proteins will facilitate the elucidation of the mechanisms of regulation of this group of enzymes and studies of their physiological roles.

7. EXAMPLE Erks, a Family of Protein-serine/-Threonine Kinase that are Activated and Tyrosine Phosphorylated in Response to Insulin and NGF 7.1. Materials and Methods 7.1.1. Isolation and Sequences Analysis of Novel ERK Genes

The QYDL probe described in Boulton et al. (1990, Science 249:64-67) was used to screen both a rat brain cDNA library constructed in the Lambda Zap II vector (Stratagene) as well as a rat genomic DNA library derived from rat (Sprague-Dawley) liver DNA partially digested with Sau3A restriction endonuclease and then cloned into the EMBL3/SP6/T7 bacteriophage vector (Clontech). After hybridization (Maisonpierre et al., 1990a, Science 247:1446-1451), the ERK2 and ERK3 phage clones were identified (and eventually purified) by washing library filters using low-normal stringency (20 mM sodium citrate, pH 7.0, 0.15 N NaCl, 0.1% sodium dodecyl sulfate (SDS) at 60° C.). The inserts in the phage clones were subcloned into Bluescript2 plasmid (Stratagene), and characterized by DNA sequence analysis using the dideoxynucleotide chain termination method (Sanger et al., 1977, Proc. Natl. Acad. Sci. U.S.A. 74:5463-6467), with the Sequenase version 2.0 kit and recommended protocols (U.S. Biochemical).

7.1.2. Generation of ERK-specific Probes

Oligonucleotides (17 bases) corresponding to the DNA sequences bordering the relatively unconserved N-terminal regions of ERK1 (amino acids 5-67), ERK2 (amino acids 14-138), and ERK3 (amino acids 11-105), were used to amplify precisely these coding regions from plasmids containing each of the ERK-cDNA inserts. The N-terminal coding regions were used because they were the least homologous regions among these three ERKs. Polymerase chain reaction (PCR) amplifications were also performed, with each pair of these primers, using either rat brain cDNA or genomic rat DNA as template. Each of these amplifications yielded indistinguishable fragments whether genomic DNA or cDNA was used, indicating that these probes did not span any introns within the ERK genes. The three fragments amplified from plasmids were each radiolabeled using the polymerase chain reaction method and hybridized to Southern blots containing rat and human genomic DNA (as described in Maisonpierre et al., 1990, Science 247:1446-1451); the filters were hybridized to each of the radiolabeled ERK-specific probes at 68° C. in the presence of 0.5 M sodium phosphate, pH 7.0, 1% bovine serum albumin (fraction V, Sigma), 7% SDS, 1 mM EDTA (Mahmoudi and Lin, 1989, Biotechniques 7:331-333) and 100 μg/ml of sonicated, denatured salmon sperm DNA, and then were washed at 68° C. as in Maisonpierre et al. (1990, Science 247:1446-1451) and subjected to autoradiography.

7.1.3. Northern Blot Analysis

Dissections of tissues and brain regions of Sprague-Dawley rats (Harlan Sprague Dawley, Inc.) were performed as described in Maisonpierre et al., 1990, Neuron 5:501-509. The dissected samples were immediately frozen in liquid nitrogen. Timed-pregnant rats were used to obtain embryonic tissues, with day of sperm positivity designated as day E1; the day of birth was designated PO. Adult rats averaged 150-275 g (6-8 weeks of age). Total RNAs were isolated by homogenization in 3M LiCl/6M urea as described in Bothwell et al., 1990, “Preparation of DNA and RNA. In Methods For Cloning and Analysis of Eukaryotic Genes”, Jones and Bartlett, Boston, Mass., pp. 15-16. Gel electrophoresis, capillary transfer to nylon membranes (MagnaGraph, Micro Separations, Inc.), and UV-cross-linking to the membranes were performed as described in Maisonpierre et al., 1990, Neuron 5:501-509. The filters were hybridized to the radiolabeled ERK-specific probes and washed as described in the preceding section. Ethidium bromide staining of triplicate gels demonstrated that equivalent amounts of total RNA were being assayed (Maisonpierre et al., 1990, Science 247:1446-1451) on each blot; this was confirmed by hybridizing several of the blots with a probe for 28S rRNA.

7.1.4. Culturing of Astro-glial Cells and P19 Embryocarcinomas

To obtain purified astroglial cell hippocampi from newborn rats were dissected, dissociated and cultured in serum-containing medium (DMEM supplemented with 10% fetal bovine serum). On culture days 7 and 9, the flasks were shaken vigorously to remove non-astroglial cells. Astroglia were then plated onto 100 mm dishes and cultured for 28 days prior to RNA preparation. The S1801A1 subclone of the P19 embryocarcinoma (McBurney et al., 1982, Nature 2999:165-167) was cultured and induced as described in Dinsmore and Solomon, 1991, Cell 64:817-826. RNA was prepared 3 days after induction.

7.1.5. Bacterial Strians and Plasmids

E. coli W3110 lac 1^(q)F⁻ a strain that overproduces the lactose operon repressor, and the plasmid vector pCP110 have been used in studies described in Panayotatos, 1988, Gene 74:357-363. Vectors were engineered for ERK2 expression by using polymerase chain reaction as follows: The 5′ synthetic oligodeoxyribonucleotide primer (RAE-21) was designed to generate a unique Sal I site immediately following the initiation methionine ATG codon by changing the sequence GTA-CGA(Val-Arg) into TCG-ACA(Ser-Thr). The 3′ primer (RAE22) included a unique Eag I site following the TAA termination codon. The expression vector pCP110 was linearized with Sal I plus Eag I and the resulting 3652 bp fragment was purified by agarose gel electrophoresis. The vector and PCR fragment similarly digested and purified were ligated and transformed in E. coli W3110 lac 1^(q)F⁻. Transformants were screened by restriction mapping for the desired plasmid and a positive candidate (pRPN117) was confirmed by DNA sequencing to carry the expected full length gene fused to the translation initiation signal in the correct reading frame.

pRPN125: This plasmid is identical to pRPN117 except that the codons of the first two amino acids were restored to the native sequence. This was accomplished with two internal PCR primers that extended over the target sequence and carried the desired modifications and two external primers that served to amplify the desired fragment. Two reactions, each with 1 μg pRPN117 as a template, were set up: one contained 5 μg RAE-10 primer and 0.5 μg RAE-28 primer and the other 5 μg RAE-22 primer and 0.5 μg RAE-27 primer. After ten PCR cycles (each cycle consisting of incubation for 1 min at 92° C., 2 min at 55° C., 2 min at 72° C.) the two samples were combined and subjected to another 25 cycles (consisting of incubation for 1 min at 94° C., 2 min at 55° C., 4 min at 74° C.) in the DNA thermal cycler. Because the internal primers RAE-28 and RAE-27 are fully complementary to each other, the products of the first stage PCR reactions can subsequently anneal. Furthermore, in the second stage reaction, the presence of substantially higher concentrations of the external primers RAE-10 and RAE-22 drives the synthesis of large amounts of the desired full-length product. The product of the final PCR reaction was purified by PAGE. A 3349 bp fragment was obtained by digesting pRPN117 with Aat II and Eag I and purified by agarose gel electrophoresis. Both fragments were ligated and transformed in E. coli W3110 lac 1^(q)F⁻. Transformants were screened by restriction mapping for the desired plasmid and one of the positive candidates (pRPN125) was further characterized by DNA sequencing across the 5′ primer region.

For fermentation, cells were shaken in LB broth at 37° C. to OD₅₉₀=1. Lactose was added to 1% final concentration and incubation continued for 20 hours. Cells were collected by centrifugation at 6,000×g for 30 min, resuspended in threefold (w/v) excess buffer A (100 mM Tris-HCl pH 7.5, 50 mM EDTA pH 8.0, 0.2 mM DTT) and stored at −20° C.

7.1.6. Purification of Recombinant ERK2

Cells (2 g) were thawed at room temperature, incubated with 2 mg of lysozyme on ice for 20 minutes and passed through a French press (SLM-Aminco) at 8000 psi. The viscous suspension was then diluted 2-fold with buffer A and further homogenized with 3 1-minute bursts of a Polytron (Kinematica) at a setting of 4. After centrifugation at 11,000×g for 10 minutes at 4° C., the supernatant was diluted 5-fold with buffer B (20 mM Hepes, pH 7.5, 0.1 mM EDTA, 2 mM dithiothreitol, and 20 mM NaCl) and applied to Affigel blue (Biorad) equilibrated in buffer B. Proteins were eluted with a 100-ml, linear gradient of 0.02-1 M NaCl in buffer B. Fractions of ERK2 (0.4-1 M NaCl) were diluted with buffer C (20 mM histidine, pH 5.6, 0.1 mM EDTA, 2 mM dithiothreitol, and 20 mM NaCl) to reduce NaCl to 0.1 M and loaded onto a DEAE-cellulose cartridge (ZetaPrep 60, CUNO) equilibrated in buffer C. The cartridge was washed stepwise with 0.1-1 M NaCl in 0.1 M increments. ERK2 eluted between 0.6 and 0.9 M NaCl and was judged to be greater than 90% pure (e.g. FIG. 7C).

7.1.7. Measurement of Recombinant ERK2 Activity

Autophosphorylation of ERK2 was carried out in the presence of 10 mM MgCl₂, 1 mM dithiothreitol, 1 mM benzamidine, 30 mM Hepes, pH 8.0, and [γ-³²P]ATP at 30° C. for 30 minutes. Kinase activity was measured by incubating ERK2 with 50 μM ATP, 20 mM MgCl₂, 1 mM dithiothreitol, 1 mM benzamidine and MBP or MAP2(0.1 mg/ml). The reactions were terminated with 10% trichloroacetic acid as in Boulton et al., 1991, Biochemistry 30:278-286.

7.1.8. Labeling, Immunoprecipitation, and Phosphoamino Acid Analysis of ERK1

Rat 1 HIRc B or PC12 cells in 2 100-mm dishes were changed to serum-free Krebs-Ringers-bicarbonate solution in 2% bovine serum albumin (Smith et al., 1980, Proc. Natl. Acad. Sci. U.S.A., 77:2641-2645) for either overnight or 60 minutes and then labeled with ³²P orthophosphoric acid (1 mCi/ml) for 50 minutes with or without the addition of insulin (0.18 μM) or NGF (75 ng/ml) for the last 5 minutes of the incubation. The cells were washed in chilled medium, scraped in 1 ml of homogenization buffer (20 mM p-nitrophenylphosphate, 20 mM Tris-HCl, pH 7.5, 1 mM EGTA, 50 mM sodium fluoride, 50 μM sodium orthovanadate and 5 mM benzamidine) containing 2 mM phenylmethylsulfonyl fluoride and 0.1 μM pepstatin, and homogenized by douncing. Following sedimentation at 100,000×g for 1 hour at 4° C., the supernatants (1 ml) were precleared once with preimmune serum and then divided for incubation with 5 μl of either antiserum 837 or preimmune serum for 1 hour on ice. Immune complexes were collected with Pansorbin (Calbiochem) and washed in homogenization buffer plus 0.2% Triton X-100 containing first 2 M NaCl, second 0.15 M NaCl, and finally 0.15 M NaCl plus 0.01% SDS. The pellets were resuspended in 40 μl of 2.5-fold concentrated electrophoresis sample buffer, boiled for 10 minutes, and loaded onto a 10% polyacrylamide gel in SDS. Aliquots (5 μl) along with an ERK1 standard were transferred to nitrocellulose to confirm by immunoblotting that the radiolabeled band in each immunoprecipitate comigrated with ERK1. For denaturing immunoprecipitations, the supernatants were adjusted to final concentrations of 0.5% SDS and 1 mM dithiothreitol. The samples were boiled 1-2 minutes and diluted 4-fold with homogenization buffer containing 1.25% sodium deoxycholate, 1.25% Triton X-100, and 0.1 or 1 mM dithiothreitol and then immunoprecipitated as above. The bands corresponding to ERK1 were excised from the dried gels and hydrolyzed in 6 N HCl for 90 minutes. Phosphoamino acids were analyzed as described by Cooper et al., 1983, “Methods In Enzymology,”, Vol. 99, J. D. Corbin and J. G. Hardman, eds, New York Academic Press, pp. 387-402.

To blot the immune complexes 1 mg of supernatant was immunoprecipitated under denaturing conditions. The Pansorbin pellets were washed twice with 0.25 M Tris, pH 7.5, and 0.1 M NaCl prior to electrophoresis. To detect phosphotyrosine the blot was stained using a monoclonal antibody to phosphotyrosine (UBI) and visualized with a goat anti-mouse IgG alkaline phosphatase-conjugated secondary antibody. The 691 immunoblot was developed with goat anti-rabbit IgG horse radish peroxidase-conjugated secondary antibody.

7.1.9. Chromatography of Extracts on Mono-Q Sepharose

PC12 cells were grown to confluence on uncoated plastic dishes in Dulbecco's Modified Eagles medium with 5% fetal bovine serum and 5% horse serum. NGF was added to 5 of 10 150-mm dishes at a final concentration of 50 ng/ml for 5 minutes. Cells were scraped into homogenization buffer and soluble fractions were prepared and protein determined as described (Boulton et al., 1991, Biochem. 30:278-286). Soluble fractions were diluted with 3 volumes of water and applied to a Mono-Q HR 5/5 column equilibrated in 50 mM β-glycerophosphate, pH 7.3, 1 mM EGTA, 1 mM dithiothreitol, 0.1 mM sodium vanadate, and 0.1 μM pepstatin. The protein was eluted with a gradient of 0-0.3 M NaCl in this buffer. Sixty 1-ml fractions were collected and assayed for MBP kinase activity using 0.3 mg/ml MBP.

7.2. Results 7.2.1. Molecular Cloning of Two Novels ERKs

The same probe utilized to isolate the ERK1 cDNA (Boulton et al., 1990, Science 249:64-65) was used to screen a rat brain cDNA library at low-normal stringency, resulting in the identification of multiple hybridizing cDNA clones. Analysis of these clones has led to the discovery of at least two novel protein kinases, which we designate ERK2 and ERK3 (FIGS. 3A (SEQ ID NO:3 AND NO:4) and 3B (SEQ ID NO:5 and NO:6)). ERK1, ERK2 and ERK3 are all more closely related to the yeast kinases, KSS1 and FUS3, than to any other protein kinases (FIGS. 4A and 4B). While the ERKs share approximately 37% (ERK3) to 56% (ERKs 1 and 2) identity with the yeast kinases, they are significantly less related (26% identity for ERK3 and 41% identity for ERKs 1 and 2) to their next closest relatives, the cdc2 family of kinases (Lee and Nurse, 1987, Nature 327:31-35). ERK1 and ERK2 are much more closely related to each other (90% identity) than to ERK3 (FIG. 2B). Using the first in-frame methionine (which satisfies the Kozak consensus for initiation sites (Kozak, 1987, Nucleic Acids Res. 15:8125-8148)), the protein predicted by the ERK2 cDNA has a molecular weight of 41.2 kDa, smaller than ERK1 (˜43 kDa), with fewer residues at the amino terminus preceding the catalytic domain. A second in-frame methionine for ERK2 can be aligned with the initiator methionines found in KSS1 and FUS3.

The deduced amino acid sequence of ERK3 predicts a protein of 62.6 kDa. While the initiator methionine is located just downstream of that predicted for ERK2, ERK3 has a C-terminal extension of approximately 180 amino acids compared to ERK1 and ERK2. Despite this long C-terminal extension, ERK3 is notably more related to ERK1 and ERK2 (˜50% identity within the catalytic domain) than to its next closest relatives (FIG. 4B). Furthermore, clusters of near identity among the ERKs (e.g. subdomains V-83% identity and VI-95% identity; see FIG. 4A) demonstrate that ERK1 and ERK2 are more closely related to ERK3 than they are to KSS1 and FUS3. Sequencing of two independent cDNA clones confirmed that ERK3 contained SPR rather than APE in subdomain VIII; the glutamic acid in the APE sequence is the only one of the fifteen invariant residues in protein kinases (Hanks et al., 1988, Science 241:42-52) which is not conserved in ERK3. Mutational analysis with the src tyrosine kinase has revealed that a lysine residue substituted for this glutamic acid leads to diminished activity (Bryant and Parsons, 1984, Mol. Cell. Biol. 4:862-866). In subdomain VI, ERK3 SEQ ID NO:6 contains DLKPAN SEQ ID NO:14, a grouping reminiscent of both tyrosine and serine/threonine kinases.

7.2.2. Evidence for Additional ERKs

We used probes specific for the individual ERKs (FIG. 5A) to determine whether or not there are additional members of this family. These probes were generated from the least conserved portions of each of the three ERKs (see Materials and Methods) and each probe was shown not to cross hybridize to the other known ERKs (FIG. 5A). The ERK1-specific probe identified a single strongly hybridizing fragment as well as several weekly hybridizing fragments in rat genomic DNA digested with EcoR1, but multiple strongly hybridizing fragments in rat genomic DNA digested with other enzymes (FIGS. 5B and 5C). The ERK2-specific probe identified two distinct EcoR1 fragments in rat genomic DNA and three distinct EcoR1 fragments in human genomic DNA (FIG. 5B). The ERK3-specific probe identified two fragments in rat genomic DNA and four fragments in human genomic DNA (FIG. 5B). Because these probes did not span any introns or contain any of the restriction sites used in the analysis (see Naterials and Methods), these hybridizations suggest that there are multiple ERKs in addition to those already isolated and that the ERKs may be further grouped into subfamilies. Screening rat genomic and cDNA libraries with the ERK-specific probes further supports the idea of subfamily members due to the isolation of a number of clones that hybridize only to one of the specific probes, but only at low-normal stringency. However, these may not all represent functional genes because partial nucleotide sequence of one of the genomic clones reveals that it contains a pseudogene closely related to ERK1 (designated ERK1Ψ, FIG. 3C).

7.2.3. Distinct Developmental and Tissue Distributions of ERKs

The ERK1-, ERK2-, and ERK-3 specific probes were used to determine the developmental and tissue distributions of ERK mRNA expression. In the adult rat all three ERK mRNAs were expressed at highest levels within the nervous system, although all the mRNAs were detectable in all tissues examined (FIG. 6A). Within the nervous system ERK2 and ERK3 displayed a clearly reciprocal pattern of mRNA expression, with higher ERK3 expression in hindbrain regions and higher ERK2 expression in forebrain regions; by comparison ERK1 was expressed more uniformly. Outside of the nervous system, each of the ERKs was expressed at highest amounts in different tissues. ERK1 was expressed at highest levels in intestine and placenta and to a lesser extent in lung. ERK2 mRNA was expressed at highest levels in muscle, thymus, and heart. The ERK2 probe identified three distinct transcripts, which were expressed at different ratios in different tissues; these transcripts may be differentially processed forms of the ERK2 mRNA or may arise from other genes in the ERK2 subfamily. ERK3 mRNA was expressed at highest levels in skeletal muscle.

A developmental study of the expression of ERK1, ERK2, and ERK3 within the nervous system revealed that ERK3 mRNA was expressed at highest levels early in development (especially in spinal cord and hippocampus), while the expression of ERK1 and ERK2 mRNAs generally increased during development (FIG. 6B). The developmental increases in the mRNAs for two of these kinases within the brain reflected changes in the amounts of ERK1 and ERK2 protein (see below). In liver and heart the expression of all three ERKs decreases in the adult rat (FIG. 6B). The discrete distributions and developmental patterns of the ERKs suggest that they play unique physiological roles in different cells or perhaps in response to different repertoires of signals.

The low levels of ERK2 and ERK3 transcripts in sciatic nerve (which contains neuronal axons and neuron-supporting cells (glia), but lacks neuronal cell bodies and thus neuronal-specific mRNA) contrasts with the high levels of ERK1 mRNA in this peripheral nerve (FIG. 6A). Thus, the high levels of ERK2 and ERK3 in the brain as opposed to peripheral nerve might reflect specific expression within neurons. To further explore this possibility, the level of each of the ERKs was compared in whole brain and in neuron-free glial cultures derived from newborn brains (FIG. 6C). The decreased level of ERK2 and ERK3 expression compared to ERK1 expression in these cultures further indicates that neuronal specificity of ERK2 and ERK3.

7.2.4. Distinct Regulation of Transcripts upon Induction of Neuronal or Muscle Differentiation in Embryocarcinoma Cells

The embryonal carcinoma line P19 normally displays an undifferentiated phenotype, but can be induced to differentiate into neuronal muscle lineages following treatment with retinoic acid (RA) or dimethylsulfoxide (DMSO), respectively (McBurney et al., 1982, Nature 2999:165-167). Transcripts hybridizing to the three ERK probes are each uniquely regulated during P19 differentiation. While ERK1 transcripts display no or a slight decrease upon induction towards either neuronal or muscle-like phenotypes, the ERK2 transcripts display a notable increase only upon neuronal induction (which parallels the pattern seen for the low affinity NGF receptor) and the ERK3 transcripts increase upon differentiation toward either the neuronal or muscle lineage. These expression patterns upon differentiation parallel the specific distributions each of the ERRS display in vivo (see above), and provide additional support for the neuronal (rather than glial) specificity of both ERK2 and ERK3. Thus, the P19 differentiation system appears to be a useful model system for studying the roles of individual ERKs during neuronal and muscle differentiation. Interestingly MAP2, which may represent a normal substrate for at least some of the ERKS, is apparently required for important features of the P19 neuronal differentiation process such as neurite extension and cessation of proliferation (Dinsmore and Solomon, 1991, Cell 64:817-826).

7.2.5. Activity of Recombinant ERK2

To begin to compare the properties of the novel ERKs with those of ERK1 purified from insulin-treated fibroblasts (Boulton et al., 1991, Biochem. 30:278-286), we purified recombinant ERK2 synthesized in E. coli (FIG. 7A). Purified recombinant ERK2 phosphorylated itself (FIG. 7C) and the exogenous substrates MAP2 and MBP in a time—(FIG. 7D) and concentration-dependent manner. The specific activities of two preparations of purified recombinant ERK2 were 0.6 and 1 nmol/min/mg of protein with either MAP2 or MBP as substrates. This compares to a specific activity with MAP2 of 300 nmol/min/mg for a highly purified preparation of ERK1 and 4 nmol/min/mg for the same ERK1 preparation which had been exhaustively dephosphorylated with the catalytic subunit of phosphatase 2a. The fact that recombinant ERK2 has a specific activity similar to that of dephosphorylated native ERK1 suggests that the recombinant protein is in the appropriate conformation to be activated by phosphorylation.

7.2.6. Antisera can Distinguish ERK1 and ERK2 and Identify a Novel ERK

Two different polyclonal antisera, both raised against a peptide consisting of the 16 C-terminal residues of ERK1 (of which 10 are conserved in ERK2), were able to distinguish between purified ERK1 and recombinant ERK2 on immunoblots and could also identify these proteins as well as a novel ERK in crude cell extracts. Antiserum 837 recognized both purified ERK1 and recombinant ERK2 (FIG. 7B), and also identified two proteins of similar sizes in crude brain extracts (FIG. 8C). Antiserum 956 recognized purified ERK1 but not recombinant ERK2; in crude brain extracts this antiserum recognized a protein comigrating with purified ERK1 as well as a novel ERK of 45 kDa (FIG. 8B). Antibodies raised against peptides from other subdomains of ERK1 also recognized all three of these proteins (Boulton and Cobb, May 1991, in Cell Regulation, Vol. II) verifying the identification of ERK1 and ERK2 and confirming the existence of a novel 45 kDa ERK. By immunoblotting, the amounts of both the 43 and the 41 kDa proteins increased dramatically (FIGS. 8B and 8C) in adult brain compared to embryonic brain, paralleling the developmentally regulated increase in accumulation of mRNAs for ERK1 and ERK2 in brain. Based on the specificities of the antisera for the purified ERKs as well as the correlations between amounts of protein and mRNA, we have designated the 43 kDa protein recognized in crude brain extracts by both antisera as ERK1, the 41 kDa protein recognized only by antiserum 837 as ERK2, and the novel 45 kDa ERK as ERK4.

7.2.7. ERKs are Phosphorylated in Response to Insulin and NGF

It has been reported that a protein cochromatographing with MAP kinase activity was phosphorylated on threonine and tyrosine residues in response to insulin (Ray and Sturgill, 1988, Proc. Natl. Acad. Sci. U.S.A. 85:3753-3757). Both types of phosphorylation may be required for maximum MAP2 kinase activity (Anderson et al., 1990, Nature 343:651-653; Ahn et al., 1990, J. Biol. Chem. 265:11495-11591; Gomez et al., 1990, FEBS Lett. 271:119-122; Boulton and Cobb, 1991, Cell Regulation, In press). We utilized our antibody reagents that specifically identify individual ERKs to explore the activation and phosphorylation state of individual members of this kinase family in response to two different growth factors, insulin and NGF.

To examine the effect of insulin and NGF on ERK1 phosphorylation directly, we used antiserum 837 to immunoprecipitate ERK1 from ³²P-labeled Rat 1 HIRcB or PC126 cells before and after insulin or NGF stimulation (FIG. 9A). Although antiserum 837 recognized ERK1, ERK2, and ERK4 on immunoblots under denaturing conditions, it immunoprecipitated the 43 kDa ERK1, a small amount of the kDa ERK4, but not the 41 kDa ERK2 from crude extracts under nondenaturing conditions. No ³²P-labeled bands were detected in immunoprecipitates from untreated cells, while ³²P-labeled ERK1 (43 kDa) and a small amount of ³²P-labeled ERK4 (45 kDa) were immunoprecipitated from both insulin-treated or NGF-treated cells, indicating that there is hormone-dependent phosphorylation of both of these ERKs (FIG. 9A). Under denaturing conditions small amounts of labeled ERK2 were also detectably precipitated following stimulation by NGF (FIG. 9B) indicating that ERK2, like ERK1 and ERK4, underwent hormone-dependent phosphorylation.

To determine if these phosphorylations include tyrosine,both phosphoamino acid analysis and phosphotyrosine immunoblotting were performed on immunoprecipitated ERKs. When duplicate immunoprecipitates (performed on Rat 1 HlRcB cells under denturing conditions (see Methods)) were immunoblotted with ERK antibodies as well as antibodies to phosphotyrosine, it was evident that both ERK1 and ERK2 from insulin-stimulated extracts contained phosphotyrosine, while there was little detectable phosphotyrosine on the proteins from the unstimulated cells (FIG. 10). No phosphotyrosine was detected on the ERK4; this could be due to our inability to detect it with the antibodies because so little of this protein was immunoprecipitated; alternatively, the hormone-induced increase in phosphate on ERK4 may be only on serine/threonine residues. Phosphoamino acid analysis of ³²P-labeled 43 kDa ERK1 excised from the gel of FIG. 9A revealed that threonine, serine, and tyrosine were phosphorylated in response to NGF (FIG. 9C). The same was true for ERK1 from insulin-treated cells. These findings demonstrate that at least three ERK proteins are phosphorylated in response to insulin and NGF and at least two of these contain phosphotyrosine.

7.2.8. Relationship Between Phosphorylation and Activation of ERKS in Response to NGF

To relate the phosphorylation of these proteins to their activities following NGF stimulation, we located ERK1 and ERK2 on immunoblots from Mono Q profiles of untreated and NGF-treated PC12 cells using antisera 956 and 837. NGF treatment resulted in a shift of elution of a portion of both ERK1 (from fractions 29-31 to fractions 38-41) and apparently also ERK2 (from fractions 25-27 to fractions 29-31) (FIG. 11), presumably due to changes in the phosphorylation of these proteins. Identical immunoblots probed with antiphosphotyrosine antibodies revealed little to no phosphotyrosine on ERK1 or ERK2 before NGF treatment. NGF treatment resulted in increased phosphorylation of tyrosine residues on both ERK1 and ERK2. Phosphotyrosine was detectable in both unshifted and shifted ERK1 protein, suggesting that multiple modifications (such as further phosphorylations on tyrosine, threonine, and/or serine residues, which would be consistent with the phosphoamino acid analysis of immunoprecipitated ERK1 described above) are required to retard elution from Mono Q. Analysis of bands from insulin-treated cells on the same gel indicated that the ERK-crossreacting and phosphotyrosine-containing bands comigrate.

NGF treatment also resulted in two major peaks of MBP kinase activity in the Mono Q profile that were not present in the profile from untreated cells. The first peak of activity coeluted with the shifted ERK2 protein (but also overlapped with the unshifted ERK1 protein), while the second peak coeluted with the shifted ERK1 protein. The first peak of MBP kinase activity was not immunoprecipitable with antiserum 837, unlike the second peak. Further, some activity from the first peak could be precipitated with an antibody to recombinant ERK2 that has a limited ability to immunoprecipitate ERK2, but none could be precipitated from the second peak. In addition, activity from both peaks could be inactivated by both the serine/threonine-selective phosphatase 2a and by the tyrosine-selective phosphatase CD45 (Boulton and Cobb, May 1991, in Cell Regulation, Vol. II). Thus, these observations support the conclusion that activity in the second peak is due to fully modified ERK1 and that in the first peak is due to activated ERK2 and not to partially modified ERK1. Altogether, the data indicate that ERK1 and ERK2 are rapidly activated in response to extracellular signals such as insulin and NGF, and that this activation is correlated with increased tyrosine phosphorylation, but that full activation requires additional modifications.

7.3. Discussion

We have compared the sequences of three members of the ERK family. Hybridizations to genomic rat and human DNA (which define a minimum of 3 new ERK genes in addition to ERKs 1, 2, and 3 in rat), screening of genomic and cDNA libraries, and immunoblotting with ERK specific antisera (which define at least one novel ERK in addition to ERK2 and ERK3) suggest that there are additional ERK genes in rat and perhaps even more in human. There is evidence for stimulation of MAP2/MBP Kinase activity in different cell types in response to a variety of signals; there is even more extensive evidence for tyrosine phosphorylation of 40-45 kDa proteins in response to cellular stimulation (cooper and Hunter, 1981, Mol. Cell. Biol. 1:165-178; Maytin et al., 1984, J. Biol. Chem. 259:12135-12143; Cooper et al., 1984, Mol. Cell. Biol. 4:30-37; Martinez et al., 1982, Mol. Cell. Biol. 2:653-685; Cooper et al, 1982, Cell 31:263-273; Roassomando et al., 1989, Proc. Natl. Acad. Sci. U.S.A. 86:6940-6943; Ferrell and Martin, 1990, Molec. Cell. Biol. 10:3020-3025; Gold et al., 1990, Nature 345:810-813). Our results indicate that the MAP2/MBP Kinase activity measured in extracts from insulin- and NGF-stimulated cells is derived not from a single enzyme but from at least two different protein kinases, ERK1 and ERK2. These data are consistent with our findings that suggest an extended family of ERK-related enzymes in rat. We conclude that similar activities found in other types of cells in response to other stimuli could be due to ERK1 or ERK2 alone, to both enzymes, or perhaps to other members of this family. The first three characterized members of this family were isolated from a brain cDNA library and are found at highest levels within the nervous system, although the expression of each ERK displays distinct tissue and developmental regulation. Screening of libraries from other tissues may yield ERKs that function predominantly in non-neural tissues.

The kinases next most closely related to the ERKs are the products of the KSS1 (Courchesne et al., 1989, Cell 58:1107-111) and the FUS3 (Ellon at al., 1990, Cell 60:649-664) genes previously cloned from yeast. KSS1 overcomes mating factor-induced growth arrest. In contrast FUS3 leads to the arrest of the cell cycle in response to mating factors. Because of regions of new identity among all three ERKS, it seems likely that they evolved from a common precursor. The relationship between the ERKs and their yeast relatives suggests that multicellular higher eukaryotes have appropriated kinases, originally utilized by primordial mating responses in unicellular organisms, to mediate responses to extracellular signals. Furthermore, the cdc2 kinases, which are the next closest relatives of the ERKS, apparently play similar roles in regulating the cell cycle in eukaryotes as diverse as yeast and man. Intriguingly, as in the case with the ERKs, the cdc2 kinases are also regulated (albeit negatively) by phosphorylation on both tyrosine and threonine.

Understanding signal transduction requires elucidating the mechanisms by which receptor-activated tyrosine phosphorylation is converted into the serine/threonine phosphorylations that regulate downstream targets. We have defined a family of serine-threonine protein kinases, the ERKS, with members that are activated and phosphorylated on tyrosine residues in response to NGF and insulin. The initiation of the series of events culminating in activation of the ERKs by insulin and NGF may occur via distinct receptors; however, both hormones are known to elicit tyrosine phosphorylation. While the insulin receptor has been recognized to contain intrinsic tyrosine kinase activity for several years, it is still unclear how activation of the NGF receptor elicits intracellular tyrosine phosphorylation. Recent evidence suggests that the NGF receptor may either contain tyrosine kinase activity (Kaplan et al., 1991, Nature 350:158-160) or is associated with such protein (Neakin and Shooter, 1991, Neuron 6:153-163). Whatever mechanisms may be involved, phosphorylation of the ERKs represents the first example of defined intracellular proteins which are phosphorylated on tyrosine in response to NGF.

Our findings suggest that a characteristic property of this family of kinases is to serve as intermediates that depend on tyrosine phosphorylation to activate serine/threonine phosphorylation cascades in response to a wide variety of extracellular signals, although it is still unclear whether the ERKs are direct substrates for receptor-associated tyrosine kinases, or whether they are further downstream in cascades. Delineating the involvement of individual ERKs in phosphorylation networks, and how they might act combinatorially, may be necessary to determine how different cell types produce the complex array of responses to the many extracellular signals that activate tyrosine phosphorylation. For example, the same signal acting through the same receptor, during different developmental stages or in different cell types, can generate dissimilar responses (e.g., proliferation vs. differentiation). Activation of specific ERKs in different contexts may contribute to multiple interpretations of the same signal or common responses to different signals. The observation that the three kinases are differentially expressed in tissues during development and the finding that ERKs 2 and 3 are induced in a model system for neuron development while ERK1 is lost during this process, further support the notion that these enzymes play unique roles in signal transduction pathways recruited during development. Furthermore, deregulation of such potentially important signalling molecules might be involved in cellular transformation and oncogenesis.

The cloning of the ERK genes and the identification of a differentiating cell line in which they are independently regulated may be used in elucidating the role of the ERKs in phosphorylation cascades, and to reveal the mechanisms involved in regulating this family of kinases. Expression of recombinant ERK proteins and their mutants may be used to define the roles of these kinases in vivo and to determine residues involved in ERK function and activation. Antibodies to common and unique regions of the ERKs may facilitate examination of how individual members participate in various responses. The indication from Mono Q profiles that both active and inactive ERK1 contains phosphotyrosine upon stimulation suggests that the extent of ERK1 activation is also determined by threonine/serine phosphorylation. The large increase in MBP kinase activity induced by okadaic acid (Haystead et al., 1990, J. Biol. Chem. 265:16571-16580), is consistent with this notion. The availability of recombinant proteins may be used to dissect the roles of both serine/threonine and tyrosine phosphorylation in ERK activation. In this regard, recombinant ERK2 has activity similar to dephosphorylated native ERK1, suggesting that the recombinant protein may be in the appropriate conformation to be activated by phosphorylation. In fact, experiments show that the activity of dephosphorylated ERK1 is increased to the specific activity of the purified active protein and the activity of recombinant ERK2 is increased 150-to 200-fold by an EGF-sensitive activator recently described by Ahn et al., 1991, J. Biol. Chem. 266:4220-4227). The ability to activate recombinant ERK2 in vitro verifies the utility of recombinant ERK proteins to search for shared or unique substrates, activators (e.g. serine/threonine and tyrosine kinases) and inactivators (e.g., phosphatases).

8. Deposit of Microorganisms

Various references are cited herein, the disclosures of which are incorporated by reference in their entireties.

The following plasmids and cell line were deposited with the American Type Culture Collection in 10801 University Boulevard, Manassas, Va. 20110-2209.

Accession No. Date of Deposit Cell line Rat 1 HIRc B CRL 10476 May 31, 1990 Plasmid pBS-rERK1 40808 May 23, 1990 Plasmid pBS-rERK2 40809 May 23, 1990 Plasmid pBS-rERK3 75009 May 14, 1991

The present invention is not to be limited in scope by the constructs deposited or the embodiments disclosed in the examples, which are intended as illustrations of a few aspects of the invention and any embodiments which are functionally equivalent are within the scope of this invention. Indeed, various modifications of the invention in addition to those shown and described herein will become apparent to those skilled in the art and are intended to fall within the scope of the appended claims.

Various references are cited herein, the disclosures of which are hereby incorporated by reference in their entireties.

21 1 1747 DNA RAT CDS (1)...(1095) ERK1 cDNA 1 agg gga act gct ggg gtc gtc ccg gtg gtc ccc ggg gag gtg gag gtg 48 Arg Gly Thr Ala Gly Val Val Pro Val Val Pro Gly Glu Val Glu Val 1 5 10 15 gtg aag ggg cag cca ttc gac gtg ggc cca cgc tac acg cag ctg cag 96 Val Lys Gly Gln Pro Phe Asp Val Gly Pro Arg Tyr Thr Gln Leu Gln 20 25 30 tac atc ggc gag ggc gcg tac ggc atg gtc agc tca gca tat gac cac 144 Tyr Ile Gly Glu Gly Ala Tyr Gly Met Val Ser Ser Ala Tyr Asp His 35 40 45 gtg cgc aag acc aga gtg gct atc aag aag atc agc ccc ttc gag cat 192 Val Arg Lys Thr Arg Val Ala Ile Lys Lys Ile Ser Pro Phe Glu His 50 55 60 caa acc tac tgt cag cgc acg ctg aga gaa atc cag atc ttg ctc gga 240 Gln Thr Tyr Cys Gln Arg Thr Leu Arg Glu Ile Gln Ile Leu Leu Gly 65 70 75 80 ttc cgc cat gag aat gtc ata ggc atc cga gac atc ctc aga gca ccc 288 Phe Arg His Glu Asn Val Ile Gly Ile Arg Asp Ile Leu Arg Ala Pro 85 90 95 acc ctg gaa gcc atg aga gat gtt tac att gtt cag gac ctc atg gag 336 Thr Leu Glu Ala Met Arg Asp Val Tyr Ile Val Gln Asp Leu Met Glu 100 105 110 acg gac ctg tac aag ctg cta aag agc cag cag ctg agc aat gac cac 384 Thr Asp Leu Tyr Lys Leu Leu Lys Ser Gln Gln Leu Ser Asn Asp His 115 120 125 atc tgc tac ttc ctc tac cag atc ctc cgg ggc ctc aag tac ata cac 432 Ile Cys Tyr Phe Leu Tyr Gln Ile Leu Arg Gly Leu Lys Tyr Ile His 130 135 140 tcg gcc aat gtg ctg cac cgg gac ctg aag ccc tcc aat ctg ctt atc 480 Ser Ala Asn Val Leu His Arg Asp Leu Lys Pro Ser Asn Leu Leu Ile 145 150 155 160 aac acc acc tgc gac ctt aag atc tgt gat ttt ggc ctt gcc cgg att 528 Asn Thr Thr Cys Asp Leu Lys Ile Cys Asp Phe Gly Leu Ala Arg Ile 165 170 175 gct gac cct gag cac gac cac act ggc ttt ctg acc gag tat gtg gcc 576 Ala Asp Pro Glu His Asp His Thr Gly Phe Leu Thr Glu Tyr Val Ala 180 185 190 aca cgc tgg tac cga gcc cca gag atc atg ctt aac tcc aag ggc tac 624 Thr Arg Trp Tyr Arg Ala Pro Glu Ile Met Leu Asn Ser Lys Gly Tyr 195 200 205 acc aaa tcc att gac atc tgg tct gtg ggc tgc att ctg gct gag atg 672 Thr Lys Ser Ile Asp Ile Trp Ser Val Gly Cys Ile Leu Ala Glu Met 210 215 220 ctc tcc aac cgg cct atc ttc ccc ggc aag cac tac ctg gac cag ctc 720 Leu Ser Asn Arg Pro Ile Phe Pro Gly Lys His Tyr Leu Asp Gln Leu 225 230 235 240 aac cac att cta ggt ata ctg ggt tcc cca tcc caa gag gac cta aat 768 Asn His Ile Leu Gly Ile Leu Gly Ser Pro Ser Gln Glu Asp Leu Asn 245 250 255 tgt atc att aac atg aag gcc cga aac tac cta cag tct ctg ccc tct 816 Cys Ile Ile Asn Met Lys Ala Arg Asn Tyr Leu Gln Ser Leu Pro Ser 260 265 270 aaa acc aag gtg gct tgg gcc aag ctt ttt ccc aaa tct gac tcc aaa 864 Lys Thr Lys Val Ala Trp Ala Lys Leu Phe Pro Lys Ser Asp Ser Lys 275 280 285 gct ctt gac ctg ctg gac cgg atg tta acc ttt aac cca aac aag cgc 912 Ala Leu Asp Leu Leu Asp Arg Met Leu Thr Phe Asn Pro Asn Lys Arg 290 295 300 atc aca gta gag gaa gca ctg gct cac cct tac ctg gaa cag tac tat 960 Ile Thr Val Glu Glu Ala Leu Ala His Pro Tyr Leu Glu Gln Tyr Tyr 305 310 315 320 gat ccg aca gat gaa cca gtg gct gag gag cca ttc acc ttt gac atg 1008 Asp Pro Thr Asp Glu Pro Val Ala Glu Glu Pro Phe Thr Phe Asp Met 325 330 335 gag ctg gat gat ctc ccc aag gag cgg ctg aag gag ctg atc ttc caa 1056 Glu Leu Asp Asp Leu Pro Lys Glu Arg Leu Lys Glu Leu Ile Phe Gln 340 345 350 gag aca gcc cgc ttc cag cca ggg gca cca gag gcc ccc taacaagaac 1105 Glu Thr Ala Arg Phe Gln Pro Gly Ala Pro Glu Ala Pro 355 360 365 agacacccct gtccttttgg acctggtctg ctctacctgc tccttctctg cagattgtta 1165 gaaaatgaac tttgctcaac ccggaccccg gcagcccagg ctggaccaag ggtgggcctg 1225 gcacccctct cactgtgctg gggtctcctc gttcaagagg cttctcccac tccagtcccc 1285 tgccccatct ccccttgacc tgagtgatga ggtggtccca gagctgatct ctgctgctgt 1345 gtctttatct atccctgcta gccccagctc tggtagacgg ttctggaatg gaagggctat 1405 gaccgcccta ggacctgtgc tacagagggg tggagggcac tgagtaggct aagctctgcc 1465 ctactcatcc tgttggaacc ccaccccatt ttccctgaca gaacattcct aaatctcaag 1525 ggctagtttc cctgaggagc cagcctaggc ctaaccctct ccctctcaag ctgccacatg 1585 taacgccctt gctgcttctg tgtgtgggtg attggatgtg gaggcggggc ccgtggagag 1645 cccgtgcccc tccccacctc cctgtgcctg tatctaatat ataaatatag agatgtgtat 1705 atggaaaaaa aaaaaaaaaa aaaaaaaaaa aaaaaaaaaa aa 1747 2 365 PRT RAT ERK1 2 Arg Gly Thr Ala Gly Val Val Pro Val Val Pro Gly Glu Val Glu Val 1 5 10 15 Val Lys Gly Gln Pro Phe Asp Val Gly Pro Arg Tyr Thr Gln Leu Gln 20 25 30 Tyr Ile Gly Glu Gly Ala Tyr Gly Met Val Ser Ser Ala Tyr Asp His 35 40 45 Val Arg Lys Thr Arg Val Ala Ile Lys Lys Ile Ser Pro Phe Glu His 50 55 60 Gln Thr Tyr Cys Gln Arg Thr Leu Arg Glu Ile Gln Ile Leu Leu Gly 65 70 75 80 Phe Arg His Glu Asn Val Ile Gly Ile Arg Asp Ile Leu Arg Ala Pro 85 90 95 Thr Leu Glu Ala Met Arg Asp Val Tyr Ile Val Gln Asp Leu Met Glu 100 105 110 Thr Asp Leu Tyr Lys Leu Leu Lys Ser Gln Gln Leu Ser Asn Asp His 115 120 125 Ile Cys Tyr Phe Leu Tyr Gln Ile Leu Arg Gly Leu Lys Tyr Ile His 130 135 140 Ser Ala Asn Val Leu His Arg Asp Leu Lys Pro Ser Asn Leu Leu Ile 145 150 155 160 Asn Thr Thr Cys Asp Leu Lys Ile Cys Asp Phe Gly Leu Ala Arg Ile 165 170 175 Ala Asp Pro Glu His Asp His Thr Gly Phe Leu Thr Glu Tyr Val Ala 180 185 190 Thr Arg Trp Tyr Arg Ala Pro Glu Ile Met Leu Asn Ser Lys Gly Tyr 195 200 205 Thr Lys Ser Ile Asp Ile Trp Ser Val Gly Cys Ile Leu Ala Glu Met 210 215 220 Leu Ser Asn Arg Pro Ile Phe Pro Gly Lys His Tyr Leu Asp Gln Leu 225 230 235 240 Asn His Ile Leu Gly Ile Leu Gly Ser Pro Ser Gln Glu Asp Leu Asn 245 250 255 Cys Ile Ile Asn Met Lys Ala Arg Asn Tyr Leu Gln Ser Leu Pro Ser 260 265 270 Lys Thr Lys Val Ala Trp Ala Lys Leu Phe Pro Lys Ser Asp Ser Lys 275 280 285 Ala Leu Asp Leu Leu Asp Arg Met Leu Thr Phe Asn Pro Asn Lys Arg 290 295 300 Ile Thr Val Glu Glu Ala Leu Ala His Pro Tyr Leu Glu Gln Tyr Tyr 305 310 315 320 Asp Pro Thr Asp Glu Pro Val Ala Glu Glu Pro Phe Thr Phe Asp Met 325 330 335 Glu Leu Asp Asp Leu Pro Lys Glu Arg Leu Lys Glu Leu Ile Phe Gln 340 345 350 Glu Thr Ala Arg Phe Gln Pro Gly Ala Pro Glu Ala Pro 355 360 365 3 1467 DNA RAT CDS (1)...(1245) ERK2 cDNA 3 ccg tgg ttc tac cgg cgg tta gtt ctc tct tct gtg ttg tcc tcc ctc 48 Pro Trp Phe Tyr Arg Arg Leu Val Leu Ser Ser Val Leu Ser Ser Leu 1 5 10 15 ctc gtt ccc gat cgc cgc cag ccg gct aca cgg gcg gcg gcg cgg ttc 96 Leu Val Pro Asp Arg Arg Gln Pro Ala Thr Arg Ala Ala Ala Arg Phe 20 25 30 ctg tgg gaa gcg cag cac aag tcg agc ggt aac gcg aag cgt cga gcc 144 Leu Trp Glu Ala Gln His Lys Ser Ser Gly Asn Ala Lys Arg Arg Ala 35 40 45 caa cgc ggc gga ggc tgt gca gcc aac atg gcg gcg gcg gcg gcg gcg 192 Gln Arg Gly Gly Gly Cys Ala Ala Asn Met Ala Ala Ala Ala Ala Ala 50 55 60 ggc ccg gag atg gtc cgc ggg cag gtg ttc gac gtg ggg ccg cgc tac 240 Gly Pro Glu Met Val Arg Gly Gln Val Phe Asp Val Gly Pro Arg Tyr 65 70 75 80 act aat ctc tcg tac atc gga gaa ggc gcc tac ggc atg gtt tgt tct 288 Thr Asn Leu Ser Tyr Ile Gly Glu Gly Ala Tyr Gly Met Val Cys Ser 85 90 95 gct tat gat aat ctc aac aaa gtt cga gtt gct atc aag aaa atc agt 336 Ala Tyr Asp Asn Leu Asn Lys Val Arg Val Ala Ile Lys Lys Ile Ser 100 105 110 cct ttt gag cac cag acc tac tgt cag aga acc ctg aga gag ata aaa 384 Pro Phe Glu His Gln Thr Tyr Cys Gln Arg Thr Leu Arg Glu Ile Lys 115 120 125 atc cta ctg cgc ttc aga cat gag aac atc atc ggc atc aat gac atc 432 Ile Leu Leu Arg Phe Arg His Glu Asn Ile Ile Gly Ile Asn Asp Ile 130 135 140 atc cgg gca cca acc att gag cag atg aaa gat gta tat ata gta cag 480 Ile Arg Ala Pro Thr Ile Glu Gln Met Lys Asp Val Tyr Ile Val Gln 145 150 155 160 gac ctc atg gag aca gat ctt tac aag ctc ttg aag aca cag cac ctc 528 Asp Leu Met Glu Thr Asp Leu Tyr Lys Leu Leu Lys Thr Gln His Leu 165 170 175 agc aat gat cat atc tgc tat ttt ctt tat cag atc ctg aga gga tta 576 Ser Asn Asp His Ile Cys Tyr Phe Leu Tyr Gln Ile Leu Arg Gly Leu 180 185 190 aag tat ata cat tca gct aat gtt ctg cac cgt gac ctc aag cct tcc 624 Lys Tyr Ile His Ser Ala Asn Val Leu His Arg Asp Leu Lys Pro Ser 195 200 205 aac ctc ctg ctg aac acc act tgt gat ctc aag atc tgt gac ttt ggc 672 Asn Leu Leu Leu Asn Thr Thr Cys Asp Leu Lys Ile Cys Asp Phe Gly 210 215 220 ctt gcc cgt gtt gca gat cca gac cat gat cat aca ggg ttc ttg aca 720 Leu Ala Arg Val Ala Asp Pro Asp His Asp His Thr Gly Phe Leu Thr 225 230 235 240 gag tat gta gcc acg cgt tgg tac aga gct cca gaa att atg ttg aat 768 Glu Tyr Val Ala Thr Arg Trp Tyr Arg Ala Pro Glu Ile Met Leu Asn 245 250 255 tcc aag ggt tat acc aag tcc att gat att tgg tct gtg ggc tgc atc 816 Ser Lys Gly Tyr Thr Lys Ser Ile Asp Ile Trp Ser Val Gly Cys Ile 260 265 270 ctg gca gag atg cta tcc aac agg cct atc ttc cca gga aag cat tac 864 Leu Ala Glu Met Leu Ser Asn Arg Pro Ile Phe Pro Gly Lys His Tyr 275 280 285 ctt gac cag ctg aat cac atc ctg ggt att ctt gga tct cca tca cag 912 Leu Asp Gln Leu Asn His Ile Leu Gly Ile Leu Gly Ser Pro Ser Gln 290 295 300 gaa gat ctg aat tgt ata ata aat tta aaa gct aga aac tat ttg ctt 960 Glu Asp Leu Asn Cys Ile Ile Asn Leu Lys Ala Arg Asn Tyr Leu Leu 305 310 315 320 tct ctc ccg cac aaa aat aag gtg ccg tgg aac agg ttg ttc cca aac 1008 Ser Leu Pro His Lys Asn Lys Val Pro Trp Asn Arg Leu Phe Pro Asn 325 330 335 gct gac tcc aaa gct ctg gat tta ctg gat aaa atg ttg aca ttt aac 1056 Ala Asp Ser Lys Ala Leu Asp Leu Leu Asp Lys Met Leu Thr Phe Asn 340 345 350 cct cac aag agg att gaa gtt gaa cag gct ctg gcc cac ccg tac ctg 1104 Pro His Lys Arg Ile Glu Val Glu Gln Ala Leu Ala His Pro Tyr Leu 355 360 365 gag cag tat tat gac cca agt gat gag ccc att gct gaa gca cca ttc 1152 Glu Gln Tyr Tyr Asp Pro Ser Asp Glu Pro Ile Ala Glu Ala Pro Phe 370 375 380 aag ttt gac atg gag ctg gac gac tta cct aag gag aag ctc aaa gaa 1200 Lys Phe Asp Met Glu Leu Asp Asp Leu Pro Lys Glu Lys Leu Lys Glu 385 390 395 400 ctc att ttt gaa gag act gct cga ttc cag cca gga tac aga tct 1245 Leu Ile Phe Glu Glu Thr Ala Arg Phe Gln Pro Gly Tyr Arg Ser 405 410 415 taaattggtc aggacaaggg ctcagaggac tggacgcgtt cagatgtcgg tgtcccccca 1305 gttcttgacc ctggtcctgt ctccagcccg tctcagctta cccactcttg actcctttga 1365 gccgttccga ggggcagtct ggtcgtagtg gcttttatac tttcacggaa ttcttcagtc 1425 cagagagttc tcctgcacca ggccctgcac agttgcactc ag 1467 4 415 PRT RAT ERK2 4 Pro Trp Phe Tyr Arg Arg Leu Val Leu Ser Ser Val Leu Ser Ser Leu 1 5 10 15 Leu Val Pro Asp Arg Arg Gln Pro Ala Thr Arg Ala Ala Ala Arg Phe 20 25 30 Leu Trp Glu Ala Gln His Lys Ser Ser Gly Asn Ala Lys Arg Arg Ala 35 40 45 Gln Arg Gly Gly Gly Cys Ala Ala Asn Met Ala Ala Ala Ala Ala Ala 50 55 60 Gly Pro Glu Met Val Arg Gly Gln Val Phe Asp Val Gly Pro Arg Tyr 65 70 75 80 Thr Asn Leu Ser Tyr Ile Gly Glu Gly Ala Tyr Gly Met Val Cys Ser 85 90 95 Ala Tyr Asp Asn Leu Asn Lys Val Arg Val Ala Ile Lys Lys Ile Ser 100 105 110 Pro Phe Glu His Gln Thr Tyr Cys Gln Arg Thr Leu Arg Glu Ile Lys 115 120 125 Ile Leu Leu Arg Phe Arg His Glu Asn Ile Ile Gly Ile Asn Asp Ile 130 135 140 Ile Arg Ala Pro Thr Ile Glu Gln Met Lys Asp Val Tyr Ile Val Gln 145 150 155 160 Asp Leu Met Glu Thr Asp Leu Tyr Lys Leu Leu Lys Thr Gln His Leu 165 170 175 Ser Asn Asp His Ile Cys Tyr Phe Leu Tyr Gln Ile Leu Arg Gly Leu 180 185 190 Lys Tyr Ile His Ser Ala Asn Val Leu His Arg Asp Leu Lys Pro Ser 195 200 205 Asn Leu Leu Leu Asn Thr Thr Cys Asp Leu Lys Ile Cys Asp Phe Gly 210 215 220 Leu Ala Arg Val Ala Asp Pro Asp His Asp His Thr Gly Phe Leu Thr 225 230 235 240 Glu Tyr Val Ala Thr Arg Trp Tyr Arg Ala Pro Glu Ile Met Leu Asn 245 250 255 Ser Lys Gly Tyr Thr Lys Ser Ile Asp Ile Trp Ser Val Gly Cys Ile 260 265 270 Leu Ala Glu Met Leu Ser Asn Arg Pro Ile Phe Pro Gly Lys His Tyr 275 280 285 Leu Asp Gln Leu Asn His Ile Leu Gly Ile Leu Gly Ser Pro Ser Gln 290 295 300 Glu Asp Leu Asn Cys Ile Ile Asn Leu Lys Ala Arg Asn Tyr Leu Leu 305 310 315 320 Ser Leu Pro His Lys Asn Lys Val Pro Trp Asn Arg Leu Phe Pro Asn 325 330 335 Ala Asp Ser Lys Ala Leu Asp Leu Leu Asp Lys Met Leu Thr Phe Asn 340 345 350 Pro His Lys Arg Ile Glu Val Glu Gln Ala Leu Ala His Pro Tyr Leu 355 360 365 Glu Gln Tyr Tyr Asp Pro Ser Asp Glu Pro Ile Ala Glu Ala Pro Phe 370 375 380 Lys Phe Asp Met Glu Leu Asp Asp Leu Pro Lys Glu Lys Leu Lys Glu 385 390 395 400 Leu Ile Phe Glu Glu Thr Ala Arg Phe Gln Pro Gly Tyr Arg Ser 405 410 415 5 3671 DNA RAT CDS (303)...(2018) ERK3 cDNA 5 agacctgccg ggcgcatatt tattcacagt tttgtcccat gttaagtcgg ttagcatagt 60 gaatctgagt gcatagtatg tcatttcatt ccgttgagtt tctcgagtgt tttctttaaa 120 tgtctgcaga gtcgctaccc ttccttgaag tatgaagcac tgcaatcttc ttaattctca 180 gtatgaagag agatttttga gctttaagtc tgaggggaac tcagcaggcc tggttggcgt 240 ctgcaatgaa catcaagaaa gcatcgtgct gtgggaatgt gatcgttttt ctcccttttt 300 ga gag atc ttt cct ttt gat gcg agt ttt ctt cct tgt tta cac aag 347 Glu Ile Phe Pro Phe Asp Ala Ser Phe Leu Pro Cys Leu His Lys 1 5 10 15 ttc aac aat ttg aaa gga aaa ggc aat tgt aag ggt ttt aaa atg gca 395 Phe Asn Asn Leu Lys Gly Lys Gly Asn Cys Lys Gly Phe Lys Met Ala 20 25 30 gag aaa ttt gaa agt ctc atg aac att cat ggc ttt gat ctg ggt tcc 443 Glu Lys Phe Glu Ser Leu Met Asn Ile His Gly Phe Asp Leu Gly Ser 35 40 45 agg tac atg gac tta aaa cca ttg ggc tgt gga ggc aat ggc ttg gtt 491 Arg Tyr Met Asp Leu Lys Pro Leu Gly Cys Gly Gly Asn Gly Leu Val 50 55 60 ttt tct gct gta gac aat gac tgt gac aaa aga gta gcc atc aag aaa 539 Phe Ser Ala Val Asp Asn Asp Cys Asp Lys Arg Val Ala Ile Lys Lys 65 70 75 att gtc ctc acc gat ccc cag agt gtc aaa cat gcc ctc cgt gaa atc 587 Ile Val Leu Thr Asp Pro Gln Ser Val Lys His Ala Leu Arg Glu Ile 80 85 90 95 aaa att att aga aga ctt gac cac gat aac att gtg aaa gtg ttt gaa 635 Lys Ile Ile Arg Arg Leu Asp His Asp Asn Ile Val Lys Val Phe Glu 100 105 110 att ctt ggt ccc agt gga agc cag ctg aca gac gat gtg ggc tct cta 683 Ile Leu Gly Pro Ser Gly Ser Gln Leu Thr Asp Asp Val Gly Ser Leu 115 120 125 aca gag ctg aat agc gtc tac att gtt cag gag tac atg gag aca gac 731 Thr Glu Leu Asn Ser Val Tyr Ile Val Gln Glu Tyr Met Glu Thr Asp 130 135 140 ttg gcg aac gtg ctg gag cag ggc cct tta ctg gag gag cat gcc agg 779 Leu Ala Asn Val Leu Glu Gln Gly Pro Leu Leu Glu Glu His Ala Arg 145 150 155 ctc ttc atg tac cag ctg ctg cgt ggg ctc aag tac atc cac tct gca 827 Leu Phe Met Tyr Gln Leu Leu Arg Gly Leu Lys Tyr Ile His Ser Ala 160 165 170 175 aac gtg ctg cac agg gat ctg aag ccg gcc aac ctt ttc att aac act 875 Asn Val Leu His Arg Asp Leu Lys Pro Ala Asn Leu Phe Ile Asn Thr 180 185 190 gaa gac ttg gtg ctg aag att ggt gac ttt ggc ctg gcc cgg atc atg 923 Glu Asp Leu Val Leu Lys Ile Gly Asp Phe Gly Leu Ala Arg Ile Met 195 200 205 gat cct cat tat tcc cat aag ggt cat ctt tct gaa gga ttg gtt acc 971 Asp Pro His Tyr Ser His Lys Gly His Leu Ser Glu Gly Leu Val Thr 210 215 220 aaa tgg tac aga tct cca cgg ctt tta ctt tct cct aat aac tat act 1019 Lys Trp Tyr Arg Ser Pro Arg Leu Leu Leu Ser Pro Asn Asn Tyr Thr 225 230 235 aaa gcg att gac atg tgg gct gca ggc tgc atc ttt gct gaa atg ctg 1067 Lys Ala Ile Asp Met Trp Ala Ala Gly Cys Ile Phe Ala Glu Met Leu 240 245 250 255 act ggt aaa acc ctc ttt gca ggt gca cat gaa ctt gaa cag atg cag 1115 Thr Gly Lys Thr Leu Phe Ala Gly Ala His Glu Leu Glu Gln Met Gln 260 265 270 ctg atc ttg gag tct atc cct gtt gtg cac gag gaa gat cgg cag gag 1163 Leu Ile Leu Glu Ser Ile Pro Val Val His Glu Glu Asp Arg Gln Glu 275 280 285 ctt ctc agc gtg att cca gtt tac att aga aac gac atg act gag cca 1211 Leu Leu Ser Val Ile Pro Val Tyr Ile Arg Asn Asp Met Thr Glu Pro 290 295 300 cac aaa ccg ctg act cag ctg ctt ccg ggg att agt cgg gaa gca ctg 1259 His Lys Pro Leu Thr Gln Leu Leu Pro Gly Ile Ser Arg Glu Ala Leu 305 310 315 gat ttc ctg gaa cag att ctg acg ttc agt ccc atg gac cgg ctg aca 1307 Asp Phe Leu Glu Gln Ile Leu Thr Phe Ser Pro Met Asp Arg Leu Thr 320 325 330 335 gcc gag gaa gca ctt tcc cat cct tac atg agc atc tac tct ttg cca 1355 Ala Glu Glu Ala Leu Ser His Pro Tyr Met Ser Ile Tyr Ser Leu Pro 340 345 350 acg gac gag cct att tcc agc cat cct ttc cac ata gaa gac gaa gtg 1403 Thr Asp Glu Pro Ile Ser Ser His Pro Phe His Ile Glu Asp Glu Val 355 360 365 gac gac att ttg cta atg gat gaa aca cac agt cac att tat aac tgg 1451 Asp Asp Ile Leu Leu Met Asp Glu Thr His Ser His Ile Tyr Asn Trp 370 375 380 gaa agg tac cac gat tgt cag ttc tcg gag cat gac tgg cct att cat 1499 Glu Arg Tyr His Asp Cys Gln Phe Ser Glu His Asp Trp Pro Ile His 385 390 395 aac aac ttt gat atc gat gag gtt cag ctt gac ccg aga gct ctg tct 1547 Asn Asn Phe Asp Ile Asp Glu Val Gln Leu Asp Pro Arg Ala Leu Ser 400 405 410 415 gat gtc acc gat gaa gaa gaa gtt caa gtt gat cct cga aag tac ttg 1595 Asp Val Thr Asp Glu Glu Glu Val Gln Val Asp Pro Arg Lys Tyr Leu 420 425 430 gat gga gac cga gag aag tat ctg gag gat ccc gcc ttc gac acg agc 1643 Asp Gly Asp Arg Glu Lys Tyr Leu Glu Asp Pro Ala Phe Asp Thr Ser 435 440 445 tac tct gct gag cct tgc tgg cag tac cca gat cac cac gag aac aag 1691 Tyr Ser Ala Glu Pro Cys Trp Gln Tyr Pro Asp His His Glu Asn Lys 450 455 460 tac tgt gat ctg gag tgt agc cac acc tgt aac tac aaa aca agg tcg 1739 Tyr Cys Asp Leu Glu Cys Ser His Thr Cys Asn Tyr Lys Thr Arg Ser 465 470 475 cca tca tac tta gat aac ctg gtg tgg agg gag agc gag gtt aac cat 1787 Pro Ser Tyr Leu Asp Asn Leu Val Trp Arg Glu Ser Glu Val Asn His 480 485 490 495 tac tat gag ccg aag ctt att ata gat ctt tcg aac tgg aaa gag caa 1835 Tyr Tyr Glu Pro Lys Leu Ile Ile Asp Leu Ser Asn Trp Lys Glu Gln 500 505 510 agt aag gac aaa tcg gac aag aga ggc aag tcc aag tgt gag agg aac 1883 Ser Lys Asp Lys Ser Asp Lys Arg Gly Lys Ser Lys Cys Glu Arg Asn 515 520 525 ggg ttg gtg aag cgg aaa ttg cgg ttg agg aag cgt ccc agc agc tgg 1931 Gly Leu Val Lys Arg Lys Leu Arg Leu Arg Lys Arg Pro Ser Ser Trp 530 535 540 ctg aga ggg aga ggg gcc aag gct ttg act ttg atg cct tca tcg cag 1979 Leu Arg Gly Arg Gly Ala Lys Ala Leu Thr Leu Met Pro Ser Ser Gln 545 550 555 gca ccg ttc agc tca gtg ccc agc gtg agt ctg gtg acg tagttgacaa 2028 Ala Pro Phe Ser Ser Val Pro Ser Val Ser Leu Val Thr 560 565 570 gttaaacgac ttgaatagct cagtgtccca gctagaaatg aaaagcctga tatccaagtc 2088 agtcagccga gaaaagcaag aaaagggaag ggctaacctg ggccagctgg gaggcttgta 2148 ccagccctcc tgggagaggg agtttgtgag tggcgggggg agtgcttcct tatcagtcag 2208 ttttgttgtg aggtcaggaa ggacgaacac gtggagaagg agaacactta caccagctat 2268 ttggacaagt tttttagcag gaaggaggat tctgaaatgc tagaaactga ggcagtggaa 2328 gaagggaagc gtggggagag aggccgygag gcaggggttc tgagcagcgg tggggagttt 2388 ctcctgagca ggcagctaga gtccataggc acgccgcagt tgcacagtgc agggggatcc 2448 ccactcaagt ccatccaggc cacgttaaca gcttcggcta tgaaatcttc ccctcaaatc 2508 gctcacaaga catacagcaa cattctgaaa catctgaact aaacactcag cagacacttc 2568 ttttgttctt catgaaatgt gttgtgtctt ttttatcact aatgttttaa gtcatttttt 2628 ttttacttga atcagaaggt gtcattaatt tgcaaggatt tttgttggtt gtcagtttgt 2688 aaaacacaaa gttttttcta catgtgagtt agttttcatt tgaagtggca tgtcgtttgc 2748 acacacacaa agaatagagc aaaacaatgc agtgcaggag gagacaagat gcgctaggat 2808 ggacagacat tctgacagag cagtgacctg cttagaggaa acaaaagctt gccttgaaac 2868 ttacacagtg agactgtaca taattgcatg aaaagatcta tttttttcct gaaacatttt 2928 tcattcatta gtattttcaa gtttttcata gtgtacagat ttgttaagac acatgatagc 2988 agcagcaact gaaaacgaat gccgaatttg gtacacatgt gttatctacc tcaaggtaac 3048 aaaagtatgg gggcgaaagc taacgcaccc atagtcgtcc ggggcatatg cacttgtatc 3108 tagcgagcgt tgggggcagt aagcaatgag actcgtgggc catttatcaa tgtcctggtg 3168 ttcatcgttt acagtgaagt gttagataca tgacatctta tttattttag caaatcagta 3228 tattttctgt atttaattat aaaaggtaac ttagtttaag ttttatttgg aagtgcggtt 3288 gttggggttt ggcactatgg tttgttgggt gccgagctga tctgagaagt cagcttgtcc 3348 cgaggctgtc catgtacgtt aagtaaagtg ctcactgtgt tataggaatc tgtattttgg 3408 gggtgcttga tctatccaca aagaaaaaaa ttaggaattt attataaaat gctgctagaa 3468 gtgttaatgg tgtttatttt ttaaaagctt gtaatgttag agttgtgtgc atggaagtga 3528 ttaaggtaca tcattattgt agtttgaaca ttgtacatga taagccttcc cccacccccg 3588 tttttactgt atgtttttat tgaatgatct attccccatc cctaggcaag catgaataaa 3648 attaggttaa atgtaaaaaa aaa 3671 6 572 PRT RAT ERK3 6 Glu Ile Phe Pro Phe Asp Ala Ser Phe Leu Pro Cys Leu His Lys Phe 1 5 10 15 Asn Asn Leu Lys Gly Lys Gly Asn Cys Lys Gly Phe Lys Met Ala Glu 20 25 30 Lys Phe Glu Ser Leu Met Asn Ile His Gly Phe Asp Leu Gly Ser Arg 35 40 45 Tyr Met Asp Leu Lys Pro Leu Gly Cys Gly Gly Asn Gly Leu Val Phe 50 55 60 Ser Ala Val Asp Asn Asp Cys Asp Lys Arg Val Ala Ile Lys Lys Ile 65 70 75 80 Val Leu Thr Asp Pro Gln Ser Val Lys His Ala Leu Arg Glu Ile Lys 85 90 95 Ile Ile Arg Arg Leu Asp His Asp Asn Ile Val Lys Val Phe Glu Ile 100 105 110 Leu Gly Pro Ser Gly Ser Gln Leu Thr Asp Asp Val Gly Ser Leu Thr 115 120 125 Glu Leu Asn Ser Val Tyr Ile Val Gln Glu Tyr Met Glu Thr Asp Leu 130 135 140 Ala Asn Val Leu Glu Gln Gly Pro Leu Leu Glu Glu His Ala Arg Leu 145 150 155 160 Phe Met Tyr Gln Leu Leu Gly Gly Leu Lys Tyr Ile His Ser Ala Asn 165 170 175 Val Leu His Arg Asp Leu Lys Pro Ala Asn Leu Phe Ile Asn Thr Glu 180 185 190 Asp Leu Val Leu Lys Ile Gly Asp Phe Gly Leu Ala Arg Ile Met Asp 195 200 205 Pro His Tyr Ser His Lys Gly His Leu Ser Glu Gly Leu Val Thr Lys 210 215 220 Trp Tyr Arg Ser Pro Arg Leu Leu Leu Ser Pro Asn Asn Tyr Thr Lys 225 230 235 240 Ala Ile Asp Met Trp Ala Ala Gly Cys Ile Phe Ala Glu Met Leu Thr 245 250 255 Gly Lys Thr Leu Phe Ala Gly Ala His Glu Leu Glu Gln Met Gln Leu 260 265 270 Ile Leu Glu Ser Ile Pro Val Val His Glu Glu Asp Arg Gln Glu Leu 275 280 285 Leu Ser Val Ile Pro Val Tyr Ile Arg Asn Asp Met Thr Glu Pro His 290 295 300 Lys Pro Leu Thr Gln Leu Leu Pro Gly Ile Ser Arg Glu Ala Leu Asp 305 310 315 320 Phe Leu Glu Gln Ile Leu Thr Phe Ser Pro Met Asp Arg Leu Thr Ala 325 330 335 Glu Glu Ala Leu Ser His Pro Tyr Met Ser Ile Tyr Ser Leu Pro Thr 340 345 350 Asp Glu Pro Ile Ser Ser His Pro Phe His Ile Glu Asp Glu Val Asp 355 360 365 Asp Ile Leu Leu Met Asp Glu Thr His Ser His Ile Tyr Asn Trp Glu 370 375 380 Arg Tyr His Asp Cys Gln Phe Ser Glu His Asp Trp Pro Ile His Asn 385 390 395 400 Asn Phe Asp Ile Asp Glu Val Gln Leu Asp Pro Arg Ala Leu Ser Asp 405 410 415 Val Thr Asp Glu Glu Glu Val Gln Val Asp Pro Arg Lys Tyr Leu Asp 420 425 430 Gly Asp Arg Glu Lys Tyr Leu Glu Asp Pro Ala Phe Asp Thr Ser Tyr 435 440 445 Ser Ala Glu Pro Cys Trp Gln Tyr Pro Asp His His Glu Asn Lys Tyr 450 455 460 Cys Asp Leu Glu Cys Ser His Thr Cys Asn Tyr Lys Thr Arg Ser Pro 465 470 475 480 Ser Tyr Leu Asp Asn Leu Val Trp Arg Glu Ser Glu Val Asn His Tyr 485 490 495 Tyr Glu Pro Lys Leu Ile Ile Asp Leu Ser Asn Trp Lys Glu Gln Ser 500 505 510 Lys Asp Lys Ser Asp Lys Arg Gly Lys Ser Lys Cys Glu Arg Asn Gly 515 520 525 Leu Val Lys Arg Lys Leu Arg Leu Arg Lys Arg Pro Ser Ser Trp Leu 530 535 540 Arg Gly Arg Gly Ala Lys Ala Leu Thr Leu Met Pro Ser Ser Gln Ala 545 550 555 560 Pro Phe Ser Ser Val Pro Ser Val Ser Leu Val Thr 565 570 7 6 PRT RAT Peptide 7 Gln Tyr Ile Gly Glu Gly 1 5 8 28 DNA RAT Oligonucleotide 8 ttctagaatt ccartayath ggngargg 28 9 6 PRT RAT Peptide 9 Asp Leu Lys Pro Ser Asn 1 5 10 31 DNA RAT Oligonucleotide 10 ttctcgagtc gacrttngan ggyttnarrt c 31 11 4 PRT RAT Peptide 11 Gln Tyr Asp Leu 1 12 6 PRT RAT Peptide 12 Gly Glu Gly Ala Tyr Gly 1 5 13 7 PRT YEAST Peptide 13 Val Pro Ser Thr Ala Ile Arg 1 5 14 6 PRT RAT Peptide 14 Asp Leu Lys Pro Ala Asn 1 5 15 549 DNA RAT CDS (1)...(549) ERK1 15 gct ccg ggg ggc ggg ggc ggg gag ccc agg gga act gct ggg gtc gtc 48 Ala Pro Gly Gly Gly Gly Gly Glu Pro Arg Gly Thr Ala Gly Val Val 1 5 10 15 ccg gtg gtc ccc ggg gag gtg gag gtg gtg aag ggg cag cca ttc gac 96 Pro Val Val Pro Gly Glu Val Glu Val Val Lys Gly Gln Pro Phe Asp 20 25 30 gtg ggc cca cgc tac acg cag ctg cag tac atc ggc gag ggc gcg tac 144 Val Gly Pro Arg Tyr Thr Gln Leu Gln Tyr Ile Gly Glu Gly Ala Tyr 35 40 45 ggc atg gtc agc tca gca tat gac cac gtg cgc aag acc aga gtg gct 192 Gly Met Val Ser Ser Ala Tyr Asp His Val Arg Lys Thr Arg Val Ala 50 55 60 atc aag aag atc agc ccc ttc gag cat caa acc tac tgt cag cgc acg 240 Ile Lys Lys Ile Ser Pro Phe Glu His Gln Thr Tyr Cys Gln Arg Thr 65 70 75 80 ctg aga gaa atc cag atc ttg ctc gga ttc cgc cat gag aat gtc ata 288 Leu Arg Glu Ile Gln Ile Leu Leu Gly Phe Arg His Glu Asn Val Ile 85 90 95 ggc atc cga gac atc ctc aga gca ccc acc ctg gaa gcc atg aga gat 336 Gly Ile Arg Asp Ile Leu Arg Ala Pro Thr Leu Glu Ala Met Arg Asp 100 105 110 gtt tac att gtt cag gac ctc atg gag acg gac ctg tac aag ctg cta 384 Val Tyr Ile Val Gln Asp Leu Met Glu Thr Asp Leu Tyr Lys Leu Leu 115 120 125 aag agc cag cag ctg agc aat gac cac atc tgc tac ttc ctc tac cag 432 Lys Ser Gln Gln Leu Ser Asn Asp His Ile Cys Tyr Phe Leu Tyr Gln 130 135 140 atc ctc cgg ggc ctc aag tac ata cac tcg gcc aat gtg ctg cac cgg 480 Ile Leu Arg Gly Leu Lys Tyr Ile His Ser Ala Asn Val Leu His Arg 145 150 155 160 gac ctg aag ccc tcc aat ctg ctt atc aac acc acc tgc gac ctt aag 528 Asp Leu Lys Pro Ser Asn Leu Leu Ile Asn Thr Thr Cys Asp Leu Lys 165 170 175 atc tgt gat ttt ggc ctt gcc 549 Ile Cys Asp Phe Gly Leu Ala 180 16 183 PRT RAT ERK1 16 Ala Pro Gly Gly Gly Gly Gly Glu Pro Arg Gly Thr Ala Gly Val Val 1 5 10 15 Pro Val Val Pro Gly Glu Val Glu Val Val Lys Gly Gln Pro Phe Asp 20 25 30 Val Gly Pro Arg Tyr Thr Gln Leu Gln Tyr Ile Gly Glu Gly Ala Tyr 35 40 45 Gly Met Val Ser Ser Ala Tyr Asp His Val Arg Lys Thr Arg Val Ala 50 55 60 Ile Lys Lys Ile Ser Pro Phe Glu His Gln Thr Tyr Cys Gln Arg Thr 65 70 75 80 Leu Arg Glu Ile Gln Ile Leu Leu Gly Phe Arg His Glu Asn Val Ile 85 90 95 Gly Ile Arg Asp Ile Leu Arg Ala Pro Thr Leu Glu Ala Met Arg Asp 100 105 110 Val Tyr Ile Val Gln Asp Leu Met Glu Thr Asp Leu Tyr Lys Leu Leu 115 120 125 Lys Ser Gln Gln Leu Ser Asn Asp His Ile Cys Tyr Phe Leu Tyr Gln 130 135 140 Ile Leu Arg Gly Leu Lys Tyr Ile His Ser Ala Asn Val Leu His Arg 145 150 155 160 Asp Leu Lys Pro Ser Asn Leu Leu Ile Asn Thr Thr Cys Asp Leu Lys 165 170 175 Ile Cys Asp Phe Gly Leu Ala 180 17 537 DNA RAT CDS (1)...(504) ERK1 psi 17 gct ccg ggg gat ggg ggc ggg gag ccc agg gga act gct ggg gtc gtc 48 Ala Pro Gly Asp Gly Gly Gly Glu Pro Arg Gly Thr Ala Gly Val Val 1 5 10 15 ctg gtg gtc ccc cgg gag gtg gag ggg cag cca ttc gac gtg ggc cca 96 Leu Val Val Pro Arg Glu Val Glu Gly Gln Pro Phe Asp Val Gly Pro 20 25 30 tgt tac aca cag ctg cag tac atc ggc gaa gat gcg gac atg gtc agc 144 Cys Tyr Thr Gln Leu Gln Tyr Ile Gly Glu Asp Ala Asp Met Val Ser 35 40 45 tca gct tat gac cac gtg cgc aag acc aga gtg gct atc aag aag att 192 Ser Ala Tyr Asp His Val Arg Lys Thr Arg Val Ala Ile Lys Lys Ile 50 55 60 agc ccc ttc gag cat caa acc tac tgt cag ccc acg ttg aga gaa acc 240 Ser Pro Phe Glu His Gln Thr Tyr Cys Gln Pro Thr Leu Arg Glu Thr 65 70 75 80 cag ata ttg ctg cga ttc cgc cat gag aat gtc ata ggc atc cga gac 288 Gln Ile Leu Leu Arg Phe Arg His Glu Asn Val Ile Gly Ile Arg Asp 85 90 95 atc ctc aga gca ccc acc ctg gaa gct atg aga gat gtt tac att gtt 336 Ile Leu Arg Ala Pro Thr Leu Glu Ala Met Arg Asp Val Tyr Ile Val 100 105 110 cag gac ctc atg gat aca gac ctg tac aag ctg ctt aag agc caa cag 384 Gln Asp Leu Met Asp Thr Asp Leu Tyr Lys Leu Leu Lys Ser Gln Gln 115 120 125 ctg agc aat gac cac atc tgc ttc ttc ctc tac cag atc ctc cgg ggc 432 Leu Ser Asn Asp His Ile Cys Phe Phe Leu Tyr Gln Ile Leu Arg Gly 130 135 140 ctc aag tac ata cac tcg gcc aat gtg ctg cac cgg gac ctg aag ccc 480 Leu Lys Tyr Ile His Ser Ala Asn Val Leu His Arg Asp Leu Lys Pro 145 150 155 160 tcc aat ctg ctt atc aac acc acc tgagacctta agatctgtga ttttggcctg 534 Ser Asn Leu Leu Ile Asn Thr Thr 165 gcc 537 18 168 PRT Artificial Sequence ERK1 psi 18 Ala Pro Gly Asp Gly Gly Gly Glu Pro Arg Gly Thr Ala Gly Val Val 1 5 10 15 Leu Val Val Pro Arg Glu Val Glu Gly Gln Pro Phe Asp Val Gly Pro 20 25 30 Cys Tyr Thr Gln Leu Gln Tyr Ile Gly Glu Asp Ala Asp Met Val Ser 35 40 45 Ser Ala Tyr Asp His Val Arg Lys Thr Arg Val Ala Ile Lys Lys Ile 50 55 60 Ser Pro Phe Glu His Gln Thr Tyr Cys Gln Pro Thr Leu Arg Glu Thr 65 70 75 80 Gln Ile Leu Leu Arg Phe Arg His Glu Asn Val Ile Gly Ile Arg Asp 85 90 95 Ile Leu Arg Ala Pro Thr Leu Glu Ala Met Arg Asp Val Tyr Ile Val 100 105 110 Gln Asp Leu Met Asp Thr Asp Leu Tyr Lys Leu Leu Lys Ser Gln Gln 115 120 125 Leu Ser Asn Asp His Ile Cys Phe Phe Leu Tyr Gln Ile Leu Arg Gly 130 135 140 Leu Lys Tyr Ile His Ser Ala Asn Val Leu His Arg Asp Leu Lys Pro 145 150 155 160 Ser Asn Leu Leu Ile Asn Thr Thr 165 19 353 PRT YEAST FUS3 19 Met Pro Lys Arg Ile Val Tyr Asn Ile Ser Ser Asp Phe Gln Leu Lys 1 5 10 15 Ser Leu Leu Gly Glu Gly Ala Tyr Gly Val Val Cys Ser Ala Thr His 20 25 30 Lys Pro Thr Gly Glu Ile Val Ala Ile Lys Lys Ile Glu Pro Phe Asp 35 40 45 Lys Pro Leu Phe Ala Leu Arg Thr Leu Arg Glu Ile Lys Ile Leu Lys 50 55 60 His Phe His Glu Asn Ile Ile Thr Ile Phe Asn Ile Gln Arg Pro Asp 65 70 75 80 Ser Phe Glu Asn Phe Asn Glu Val Tyr Ile Ile Ile Gln Glu Leu Met 85 90 95 Gln Thr Asp Leu His Arg Val Ile Ser Thr Gln Met Leu Ser Asp Asp 100 105 110 His Ile Gln Tyr Phe Ile Tyr Gln Thr Leu Arg Ala Val Lys Tyr Val 115 120 125 Leu His Gly Ser Asn Val Ile His Arg Asp Leu Lys Pro Ser Asn Leu 130 135 140 Leu Ile Asn Ser Asn Cys Asp Leu Lys Val Cys Asp Phe Gly Leu Ala 145 150 155 160 Arg Ile Asp Glu Ser Ala Ala Asp Asn Ser Glu Pro Thr Gly Gln Gln 165 170 175 Ser Gly Met Thr Glu Tyr Val Ala Thr Arg Trp Tyr Arg Ala Pro Glu 180 185 190 Val Met Leu Thr Ser Ala Lys Tyr Ser Arg Ala Met Asp Val Trp Ser 195 200 205 Cys Gly Cys Ile Leu Ala Glu Leu Phe Leu Arg Arg Pro Ile Phe Pro 210 215 220 Gly Arg Asp Tyr Arg His Gln Leu Leu Leu Ile Phe Gly Ile Ile Gly 225 230 235 240 Thr Pro His Ser Asp Asn Asp Leu Arg Cys Ile Glu Ser Pro Arg Ala 245 250 255 Arg Glu Tyr Ile Lys Ser Leu Pro Met Tyr Pro Ala Ala Pro Leu Glu 260 265 270 Lys Met Phe Pro Arg Val Asn Pro Lys Gly Ile Asp Leu Leu Gln Arg 275 280 285 Met Leu Val Phe Asp Pro Ala Lys Arg Ile Thr Ala Lys Glu Ala Leu 290 295 300 Glu His Pro Tyr Leu Gln Thr Tyr His Asp Pro Asn Asp Glu Pro Glu 305 310 315 320 Gly Glu Pro Ile Pro Pro Ser Phe Phe Glu Phe Asp His His Lys Glu 325 330 335 Ala Leu Thr Thr Lys Asp Leu Lys Lys Leu Ile Trp Asn Glu Ile Phe 340 345 350 Ser 20 368 PRT YEAST KSS1 20 Met Ala Arg Thr Ile Thr Phe Asp Ile Pro Ser Gln Tyr Lys Leu Val 1 5 10 15 Asp Leu Ile Gly Glu Gly Ala Tyr Gly Thr Val Cys Ser Ala Ile His 20 25 30 Lys Pro Ser Gly Ile Lys Val Ala Ile Lys Lys Ile Gln Pro Phe Ser 35 40 45 Lys Lys Leu Phe Val Thr Arg Thr Ile Arg Glu Ile Lys Leu Leu Arg 50 55 60 Tyr Phe His Glu His Glu Asn Ile Ile Ser Ile Leu Asp Lys Val Arg 65 70 75 80 Pro Val Ser Ile Asp Lys Leu Asn Ala Val Tyr Leu Val Glu Glu Leu 85 90 95 Met Glu Thr Asp Leu Gln Lys Val Ile Asn Asn Gln Asn Ser Gly Phe 100 105 110 Ser Thr Leu Ser Asp Asp His Val Gln Tyr Phe Thr Tyr Gln Ile Leu 115 120 125 Arg Ala Leu Lys Ser Ile His Ser Ala Gln Val Ile His Arg Asp Ile 130 135 140 Lys Pro Ser Asn Leu Leu Leu Asn Ser Asn Cys Asp Leu Lys Val Cys 145 150 155 160 Asp Phe Gly Leu Ala Arg Cys Leu Ala Ser Ser Ser Asp Ser Arg Glu 165 170 175 Thr Leu Val Gly Phe Met Thr Glu Tyr Val Ala Thr Arg Trp Tyr Arg 180 185 190 Ala Pro Glu Ile Met Leu Thr Phe Gln Glu Tyr Thr Thr Ala Met Asp 195 200 205 Ile Trp Ser Cys Gly Cys Ile Leu Ala Glu Met Val Ser Gly Lys Pro 210 215 220 Leu Phe Pro Gly Arg Asp Tyr His His Gln Leu Trp Leu Ile Leu Glu 225 230 235 240 Val Leu Gly Thr Pro Ser Phe Glu Asp Phe Asn Gln Ile Lys Ser Lys 245 250 255 Arg Ala Lys Glu Tyr Ile Ala Asn Leu Pro Met Arg Pro Pro Leu Pro 260 265 270 Trp Glu Thr Val Trp Ser Lys Thr Asp Leu Asn Pro Asp Met Ile Asp 275 280 285 Leu Leu Asp Lys Met Leu Gln Phe Asn Pro Asp Lys Arg Ile Ser Ala 290 295 300 Ala Glu Ala Leu Arg His Pro Tyr Leu Ala Met Tyr His Asp Pro Ser 305 310 315 320 Asp Glu Pro Glu Tyr Pro Pro Leu Asn Leu Asp Asp Glu Phe Trp Lys 325 330 335 Leu Asp Asn Lys Ile Met Arg Pro Glu Glu Glu Glu Glu Val Pro Ile 340 345 350 Glu Met Leu Lys Asp Met Leu Tyr Asp Glu Leu Met Lys Thr Met Glu 355 360 365 21 297 PRT Homo sapiens 21 Met Glu Asp Tyr Thr Lys Ile Glu Lys Ile Gly Glu Gly Thr Tyr Gly 1 5 10 15 Val Val Tyr Lys Gly Arg His Lys Thr Thr Gly Gln Val Val Ala Met 20 25 30 Lys Lys Ile Arg Leu Glu Ser Glu Glu Glu Gly Val Pro Ser Thr Ala 35 40 45 Ile Arg Glu Ile Ser Leu Leu Lys Glu Leu Arg His Pro Asn Ile Val 50 55 60 Ser Leu Gln Asp Val Leu Met Gln Asp Ser Arg Leu Tyr Leu Ile Phe 65 70 75 80 Glu Phe Leu Ser Met Asp Leu Lys Lys Tyr Leu Asp Ser Ile Pro Pro 85 90 95 Gly Gln Tyr Met Asp Ser Ser Leu Val Lys Ser Tyr Leu Tyr Gln Ile 100 105 110 Leu Gln Gly Ile Val Phe Cys Ile His Ser Arg Arg Val Leu His Arg 115 120 125 Asp Leu Lys Gln Asn Leu Leu Ile Asp Asp Lys Gly Thr Ile Lys Leu 130 135 140 Ala Asp Phe Gly Leu Ala Arg Ala Phe Gly Ile Pro Ile Arg Val Tyr 145 150 155 160 Thr His Tyr Val Val Thr Leu Trp Tyr Arg Ser Pro Glu Val Leu Leu 165 170 175 Gly Ser Ala Arg Tyr Ser Thr Pro Val Asp Ile Trp Ser Ile Gly Thr 180 185 190 Ile Phe Ala Glu Leu Ala Thr Lys Lys Pro Leu Phe His Gly Asp Ser 195 200 205 Glu Ile Asp Gln Leu Phe Arg Ile Phe Arg Ala Leu Gly Thr Pro Asn 210 215 220 Asn Glu Val Trp Pro Glu Val Glu Ser Leu Gln Asp Tyr Lys Asn Thr 225 230 235 240 Phe Pro Lys Trp Lys Pro Gly Ser Leu Ala Ser His Val Lys Asn Leu 245 250 255 Asp Glu Asn Gly Leu Asp Leu Leu Ser Lys Met Leu Ile Tyr Asp Pro 260 265 270 Ala Lys Arg Ile Ser Gly Lys Met Ala Leu Asn His Pro Tyr Phe Asn 275 280 285 Asp Leu Asp Asn Gln Ile Lys Lys Met 290 295 

What is claimed is:
 1. A purified MAP2 protein kinase comprising an amino acid sequence as set forth in SEQ ID NO:2.
 2. The purified MAP2 protein kinase of claim 1, having an amino acid sequence as set forth in SEQ. I.D. No.
 2. 3. A purified MAP2 protein kinase designated ERK1 encoded by a nucleic acid molecule selected from the group consisting of: (a) a nucleic acid molecule comprising a nucleotide sequence as set forth in SEQ ID NO:1; and (b) a nucleic acid molecule comprising a nucleotide sequence that, as a result of the degeneracy of the genetic code, differs from the nucleotide sequence of (a) and encodes the MAP2 protein kinase designated ERK1 as set forth in SEQ ID NO:2.
 4. A purified MAP2 protein kinase designated ERK1 encoded by the plasmid designated pBS-rERK1 (ATCC® Accession No. 40808). 